Hey gang
Been away for a few days
OK, as best as I can remember for the Somerville bikes (that smoky shop thing again

)
When I started there in late '86, the numbering scheme was simply the year and the frame number for that year
example: 86105 would stand for the 105th frame built in 1986. There was no distinguishing models or sizes in the serial numbers then
My 1987 Wicked is SN 87777. I told Reggie to put 777 aside for me when he got to it and he did. I held on the BB until it was time to build my 18.
In '88 (I think), Chris wanted to distinguish between Fats, Wickeds, and Team Comps, so we simply added an F, W, or T at the end of the serial number (It's possible Team Comps could have been TC

)
When the Yo Eddy was added to the line-up, the numbering was again changed. We went to putting the number of each model built as the serial number and I believe the size was also added but that may have come after. (? Sorry)
example a serial number with Y105S would stand for a small Yo and that was number 105 Yo that was built that year, there could also be a W105 which would have been the 105th Wicked built that year. (You were close Sette)
The position of the year designator and size designator may and probably did vary. The Somerville serial numbers were tracked in a simple notebook that was controlled by the tacking department. I don't believe that information was ever transposed to an electronic file on the computer. Given what I know now and how everyone wants the accurate information, I really wish I had done that and kept track of each bike that I worked on. At the time, it didn't seem that important.
It still amazes me that these bikes have become such collector's items. Had I only known...
It's riding season! I actually put about 10 miles on the TI bike a couple of weeks ago.
enjoy the spring
Scott