A Washington investment company that promised "a once-or-twice-in-a-lifetime" chance to make mathematically astronomical returns" by speculating in Mexican pesos was charged with fraud yesterday by the Commodity Futures Trading Commission.

Capital Cities Currency Corp. failed to warn investors that their entire investment could be wiped out if the value of the peso fell as little as one-third of a cent, the CFTC charged.

The company also failed to register with the CFTC as required by law, ignored several other federal commodity regulations and used "schemes to defraud" its customers, the CFTC charged in a five-count civil lawsuit filed in U.S. District Court here.

Capital City Currencies collected at least $174,000 from investors, according to the complaint, which asks the court to step in and protect the money of investors.

The company's offices are at 1901 Pennsylvania Ave. NW., only a few blocks from CFTC headquarters at 20th and K Streets NW.

Kevin R. Suplain, secretary-treasurer of CCCC, said the company would respond today to the CFTC charges.

Kevin Duplain was named a defendant in the CFTC lawsuit along with David M. King, vice president of CCCC and manager of its Washington office; Alfred A. Duplain of Richardson, Tex., president of the company; and Richard G. Gonday of Dallas, the company's pool manager.

Beside its Pennsylvania Avenue headquarters, the CCCC has offices in Mesquite and Arlington, Tex., Oklahoma City and Jackson, Miss.

CFTC officials said the lawsuit was the first ever filed against operators of a commodity pool, a relatively new form of futures market investment. In a commodity pool, several investors pool their funds to buy futures contracts.

Under the CCCC plan, the CFTC said each investor put from $600 to $1,600 into the pool. One-third of the money went to CCCC as a "risk assumption fee," and the company also was to get 25 percent of any profits the investors made.

The 33 1/3 percent "risk assumption fee" uas "to insulate participants from risk beyond their original investment," CCCC allegedly told investors.

CCCC's promotional literature claimed that Swiss bankers expect the Mexican peso, now worth 4.3 cents, to be worth as much as the American dollar within 10 years. "If the Swiss are right (and our research disagrees only with the timing; we believe it will happen sooner), there will be a ton of profit in pesos," CCCC said.

By investing $15,000 in futures contracts for 3 million pesos, the pool could make a $30,000 profit every time the peso increased in value by a penny, the company said.

What the company didn't tell investors was that if the peso's value dropped by 1/3 cent, the entire investment could be wiped out, said CFTC auditor Adelaide Blitzer in an affidavit filed with the complaint.

Failure to disclose the downside risk of a commodity investment is a violation of the law, the CFTC said.

The complaint accused CCCC of falsely claiming to be licensed by the Chicago Board of Trade and the Chicago Mercantile Exchange, when those registrations expired before CCCC began touting its peso pool in April.