Sherlock Holmes, go home.
In ''the case of the counterfeit tokens,'' as some have dubbed it, the chief culprit may be the State of Connecticut.
The case began about a month ago when the 17 1/2-cent Connecticut Turnpike tokens began turning up in New York City subway turnstiles. The Connecticut token is just a fraction (5/1000 of an inch) larger than the city subway tokens, which cost 75-cents each, but the ''counterfeit'' token fits easily into the turnstiles.
Since Oct. 16, Connecticut tokens have been finding their way into city turnstiles. Sales boomed at eight Connecticut Turnpike toll booths when it became common knowledge last week that they worked in the NYC subway turnstiles as well.
But the other side of the coin is that the culprit state also has suggested a way to solve the problem. Connecticut transportation officials have offered to coat their 10 million tokens with a nickel alloy, if the New York Transit Authority (TA) installs magnets in the turnstiles to reject the imposters.
Connecticut Transportation Commissioner William Burns plans to meet this week with TA officials to discuss the proposal - and how much it will cost.
Ironically, says Edmund Mickiewicz, spokesman for the Connecticut Transportation Department, ''the same mint minted both coins.'' In his view, it was the mint's mistake. But he also said state officials should have compared sizes before selling the tokens.