LAST JUNE 3 on Spain's northwest coast, an aging croupier dropped a marblesized ivory ball into a roulette wheel he had started spinning. The croupier's name wasn't important, but his act was. He was the last croupier to drop a ball onto a roulette wheel before casino gambling was banned in Spain more than half a century ago. His act on the island of La Toja symbolized its return.

Legalized gambling is one of the latest manifestations of the new era spawned in Spain by the death of 36-year dictator Generalisimo Francisco Franco on Now. 20, 1975. King Juan Carlos I, although designated by Franco as his successor, quickly abolished many of Franco's puritanical edicts. A newly ratified constitution codifies many other reforms.

As one Spaniard put it: "Franco is dead. We are free now."

The Spanish in general have responded to their new freedom with the uusual Lation gusto. Under Franco, sex was rarely mentioned in public, Post-Franco newsstands, movie billboards and advertisements throughout Spain display sex more explicitly than would be tolerated in the United States, although in line with the rest of Western Europe. The new national lottery also has been extremely popular, so it was natural that Spain would join the rest of Europe in legalizing gambling.

It was more than just a new freedom in Spain's case. The phaseout of gambling actually began under the previous dictator, Primo de Rivera, in 1925, so Spain had to watch for 53 years as surrounding countries such as Portugal, France and Monaco reaped millions from the world's gamblers.

Spain's economy is heavily dependent on the tourist dollar. Although Spain always has been a popular nation for tourists, the government apparently assumed it could do better by offering gambling. Perhaps it was a decision aimed more at preserving tourism than increasing it. One of the new reforms has been the relaxation of government regulations, such as the control of hotel prices. With control soon to be eased, one of Spain's attractions -- being one of the cheapest European countries to visit -- may evaporate.

Other factors were important, however, and gave rise to the odd locations of the gambling casinos, "casinos de juego" in Spanish. The government viewed gambling as one way to expand tourism into seldom-visited spots and to redistribute some of the nation's wealth. Thus, when plans for a legalized gambling system were formulated within a year of Franco's death, 18 casinos were authorized. Primary considerations in granting Spanish licenses for casinos were: "tourist density of the site, technological location, guarantees and quality." No two casinos can be near each other, no more than two may be located in a single province and none can be located in a large city.

These provisos could discourage any increase in the already meager American patronage of the casinos, since Americans tend to stay in governmentrun paradores or in larger cities where American-style comfort is offered. Also, all of the casinos opened thus far are practically out of reach to anyone without a car.

And not surprisingly, the first five to open and the two expected to open next are either attractively close to the French or Portuguese borders to beckon foreign gamblers, or near the beach resorts.

The first casino, Casino de La Toja, is about 40 rough driving miles southwest of Santiago de Cospostela and about the same distance from the Portuguese border. Then came Nuevo Gran Casino de Kursaal de San Sebastian, outside the northern coastal city of San Sebastian, only about 12 miles from the French border; and the Casino Nueva Andalucia de Marbella at Marbella, near the western end of the Costa del Sol.

Indicative of the mad scramble by casino owners to get their doors open were the next two. One casino, at Lioret de Mar, north of Barcelona on the Costa Brva and 50 miles from the southern border with France, opened as soon as it got a table and well before it could offer full operation.Another, on Mallorca, opened in temporary quarters in a golf club until it spermanent building can be completd. Also now open are the Gran Casino de El Sardinero, in the north os Spain, and Azarmenor at San Javier, Murcia, in the east.

Expected to open next are casinos at Perelada, in the northeast corner seven miles from the French line, and at Benalmadena, a casino-hotel complex just south of Torremolinos at the center of Spain's winter tourist trade on the Costa del Sol. A casino at Torrelodones, on the highway from Madrid to El Escorial, has been delayed by an apparent dispute over the membership of the group setting it up. Eigfht more authorized casinos, not yet close to opening, will be spread throughout the country.

The training of croupiers and the international influence on the operation of each casino depend primarily on where it is located. La Toja used help from the casino at Estoril near Lisbon. Banco Pastor, the huge Galician bank that owns La Toja, is the money behind the Casino La Toja Sociedad Anonyma that runs the casino.

Jose Rogelio Diaz Chao, assistsnt director of the casino, called the Estoril casino "the father of Casino La Toja." The casino used Estoril's croupiers to train 68 Spanish croupiers for La Toja in one of the adjacent hotels while the casino was being readied for its June opening. Thirty-two would-be croupiers are still in training.

Because of its location, La Toja numbers Spanish, Portuguese, German and French among its most numerous customers, in that order. Chao said the casino has seen only a few Americans. At least one of the two croupiers at each table can of the two croupiers at each table can speak Galician (a thick, lisping Spanish dialect), Spanish or Portuguese. But there always is a croupier in the building who can speak English, German or Italian if an explanation of the gambling rules is needed.

Whilt La Toja depended on the Portuguese for aid, the casino near San Sebastian and the one on emallorca used French help. The ones at Lloret de Mar and Marbella use English to train personnel and give advice on setting up the operation.

Foreign investment, however, is limited to 25 percent of the casino capital, and foreigners can comprise no more than one-fifth of the staff after three years of operation. The casino must have more than $3 million in assets.

Also discouraging to foreign investment is the government casino tax. The government may tax up to 50 percent of the gross earnings of a large operation. Gross means the customer losses and the required admission charge, minus the winnings of the customers. Chao estimated that La Toja taxes would be 85 percent of net profits.

There have been reports that wealthy Americans like bandleader Xavier Cugat want to invest in Spanish gambling but have been pointedly discouraged by the Spanish government. Officials also fear the Mafia may try to invade the gambling scene.

Procedures a customer is likely to encounter are evidence of government controls. Two government employes are stationed in each casino during its operation g hours. To weed out undesirables, the government representatives from the Interior Department that also employs the once-dreaded Guardia Civil check identification such as ID cards of Spaniards and the passports of foreigners.

Interestingly, among those prohibited to play n Spanish casinos are "civil or military administrators responsible for public funds." Others barred include anyone under 21, persons appearing on the international gambling blacklist (called the "red list" in Spain), anyone legally declared bankrupt or guilty of fraud, persons on parole, "suspicious persons," persons who appear drunk or mentally ill, "potential troublemakers and anyone who is likely to disturb the normal running of the games," people with arms or dangerous objects and people banned as chronic gamblers by the national gaming board at the request of their families.

American gamblers who have never played in a foreign casino probably would notice first that the predominant tables differ from those at home. Certain games are as popular at La Toja as at typical European casinos. French roulette is preferred by far over American roulette at La Toja. Since Americans haven't caught on to Spanish casinos, crap tables sit idle. One-armed bandits are authorized by the government, but there is no rush to install them. La Toja will have a small room of them soon, taking 50,25 and two 5-peseta pieces (a peseta equals about 1 1/2 cents).

The American gambler also will note the Spanish style of understated opulence at casinos such as La Toja. It is closer to that of the staid Puerto Rico hotel casinos than the noise and garish decor of Nevda casinos. What opulence there is at La Toja is tasteful, from the 1764 Neilson tapestry hanging on one wall of the foyer to the 1817 rug on the floor and Czechoslovakian crystal chandelier above it.

Outside, La Toja appears small, with three yellow canopies covering the drive-up entrance. The low, squat building, built around the turn of the century as a small Galician palace, is dwarfed by one of the island's three resort hotels. Beyond the casinto building are the waters of the Rio d Arosa, largest of the four large inlets that break up the western Atlantic Xoast of Spain southwest of the centuries-old pilgrim center of Santiago de compostela.

Two uniformed guards wearing sidearms walk about the outside of the building while two liveried doormen greet cars that roll up to the steps to disgorge the "clients." Inside, the client is greeted by one of the plentiful casino employes and ushered to a small cubicle.

At the cubicle, the visitor must hand over his passport and wait while the staff thumbs through the thouwands of names in a file to be sure the visitor is not an undesirable. The file is kept up to date by a computerized operation in the Madrid headquarters of the gaming board, which trades names with other gambling countries. If the visitor passes, he'll be sold an admission card for at least 200 pesetas, depending upon the duration of the ard. The cheapest is for one day, the most expensive is 5,000 pesetas, good for one year.

In the main gambling area are four French roulette tables. A low balcony at one end holds two American roulette tables, a similar balcony at the other end has a small bar and lounge. Drinks are permitted at the tables. Upstairs are blacjack and baccarat tables. Below the first floor are the craps tables, where the slot machines also will be put. The entire gambling area is no larger than the area devoted to slot machines alone at the MGM Grand Hotel in Las Vegas. But assistant casino director Chao said that during the summer resort season, La Toja counted as many as 1,500 clients on weekends. Weekdays would draw 700 to 800.

Betting ranges from a 100-peseta ($1.50) minimum in both American and French roulette to a 200,000-peseta $3,000) maximum on even bets in French roulette. The main difference in the roulettes is that an American wheel adds a double Zero -- increasing the house's chances.

Blackjack and three forms of baccarat -- punto y baca, 30-40, and chemin de fer -- also are available. Chemin defer, as in other European casinos, is by far the most popular form. It's faster version of baccarat, thus the name which means "railroad" in French.

The London company of Jaymers Ltd. has cornered the market on the manufacture of gaming furniture in Spain, through its subsidary, Iserco, on Mallorca. So far, all Spanish equipment except roulette wheels (French and English made) is made by Iserco.

The 5 o'clock opening hour arrived as we finished our tour with Chao, and several Spaniards entered and headed for one of the French roulette tables. Although our visit was during the offseason at the La Toja resort, they wore casual but stylish clothes. Later in the evening, after 9, men would be expected to wear jackets, though not necessarily a tie during hot summer months.

Most of the casinos will have the rules of the games printed in several languages. At least in their treatment of English, Spanish translations can sometimes be too literal. La Toja attempted to translate in the rules for chemin de fer, "En caso empate, la jugada es considerada nula," which means, "In case of a draw, the game is considered void."

La Toja translated it: "the game is considered useless."