[carguychris]

You probably don't need to bother with the history letter, at least to find the production date. Guns with the post-1982 3-letter 4-number serial number style are usually in S&W's computer database and can be looked up by customer service.

Also, the Standard Catalog of Smith & Wesson indicates that the TCB prefix was used in 1988 and the TED prefix was used in 1989; the TDT prefix theoretically falls between those, so let's say 1988-1989.