If W.C. Fields had been around on his 100th birthday, yesterday, he would have been delighted to know the U.S. Postal Service had to pay his heirs $2,023 to issue a stamp in his honor.

The Postal Service was caught with its stamps already down for its 1980 program when they were contacted by Roger Richman, representing W. C. Fields Productions Inc., and both agreed on a check for that amount. wIt was the first time the Postal Service ever had to pay for permission to issue a likeness on a stamp.

In a closely worded contract the Postal Service was advised that the Fields heirs have the full right to control and license the use of the name, voice, likeness and image of their relative.

"There is a moderate amount of money coming in from the various enterprises," Richman said. "Six people make up Fields Inc. -- his son, daughter-in-law and the four grandchildren."

Contrary to the lovely, loose reputation that Fields nurtured about not knowing where his money was planted around the country as he moved through a vague, boozy life. Richman said, "He knew where every cent was and the day the interest was due."

His grandson Ronald Fields said, "W.C. Fields was a pioneer in merchandising himself and some of the contracts he signed are still being used by agents to protect their acting clients."

"Fields was one of the first actors to merchandise himself and withhold his rights from the movie companies," Richman said. "I have a contract here that he signed when he made David Copperfield and he did not merchandise himself to a studio."

Fifteen licensed companies are now allowed to produce records, vintage radio tapes, his image on plates, shot glasses, spoons, party invitations, napkins, coins dolls, dummies, busts and dart games.

"His heirs are interested in carrying on his tradition," Richman said. "Fields is a very valuable property, 'W.C. Fritto's (a cornchip product) had been licensed by the family to use the name. We want to retain quality and a fond memory."

Richman thought the post office fee of $2,023 was not enough and said, "We had no idea and were the last to be told the stamp was coming out.

"Cachetmakers will sell a million first-day covers running anywhere from 60 cents to $40. My clients are not making more than that. We probably did not get as much as the desidered."

Don McDowell, a spokesman for the Postal Service said, "We paid New York artist Jim Sharp to design the stamp and paid him $1,500. That is our standard fee.

"When the stamp was suggested we had no idea W.C. Fields Productions existed. We never heard of the estate.

"They suggested a fee and we paid them," he said. Wondering about who else may have to be paid on future stamps McDowell said, "When people die we recieve a lot of letters suggesting stamps.

"Unless you're a president, 10 years have to elapse before you can appear on a stamp. John Wayne is being considered."

The Performing Art Series of which the Fields stamp will be part began in 1978. A Will Rogers stamp came out last November, follwed by George M. Cohan, and Jimmie Rodgers, a country music star.

"We have had stamps of Albert Einstein and John Steinbeck," McDowell said, "but this is the first time we encountered something like this."

Fields could have only laughed at all this while heading for a nearby saloon.

Last night 1,100 people packed a hall at the Academy of Motion Pictures to celebrate the 100th anniversary of Fields' birth as William F. Bolger, postmaster general, delivered a speech from President Carter.

The whole situation moved grandson Ronald Fields to show mock dismay as he said. "Apparently the post office did not follow through with some of our suggestions when we suggested a martini flavored glue."

But he should have remembered a few last words of hte actor/comedian who spent a career making people laugh by his drunken antics, when he said "The only thing I regret is that I never had a hangover. I wonder what it would have been like without drinking."