Maybe yes, maybe no. Mine is a 1981, 6xx with serial number beginning with an "N", hence my question. According to the Vintage Trek website:

"The Japanese Connection - Beginning in 1981 or 1982 (and extending through at least 1986), Trek used Tange, a subcontractor in Japan, to build some frames and parts of frames. The 300 and some 400 series were a complete (unpainted) frame and fork from Japan, but painted and assembled in Waterloo. The 500, 600, and 800 (MTB) series had the main triangle built in Waterloo, the pre-assembled rear stays were attached, and the whole works painted and assembled in Waterloo. The 700, 900, and 170 series were completely built, painted, and assembled in Waterloo. Some 600 series were all Reynolds 531 frames. Trek had Reynolds seatstays and chain stays shipped from England to Japan, where they were assembled into the rear triangle assemblies and then shipped to Waterloo to be attached to the main frame." Vintage Trek - Steel Road Bike Timeline, Trek Bicycle Corporation

And more to the point, this: "It is likely these frames, SNs beginning with M or N (Models 41x and 61X), were contracted out or were made in a separate Trek facility, and were given the old serial number form so as not to interfere with the sequential numbers being assigned by Trek in their main shop, which began in late 1980." Vintage Trek Bicycle Frame Serial Numbers, bike