I have a Fat Chance I bought back in about 1987/88. The serial #86688
I bought the bike on discount marked down from $1200. to $800. I am thinking it is a 1987, but not sure if number corresponds to the year.
Your frame is a 1986 model. Most likely a Fat Chance (we called them "regular" Fats) It would have been the 688th frame produced in 1986. It was probably right around when I started with them (November 1986). Not sure who welded the frame but it could be one of Gary Helfrich's last Fat Chance frames that he welded before he left to start Kestrel Metal Works across the courtyard from Fat City. Yes, most people think he started Merlin but the original name was Kestrel. He lost the right to the name to another startup bike company that was producing carbon fiber frames and had already trademarked it. He found that a Merlin was another type of small hawk (like a kestrel) so he didn't have to change the logo, other than the name and Merlin was also associated with wizardry.
Your frame most likely has seatstay-mounted cantilever brake mounts and brazed-on cable guides on the top of the bottom bracket. Those were eliminated in favor of the riveted plastic guide that attached to the bottom of the bottom bracket in 1987.
The Wicked was introduced in 1987 and I went full-time with Fat City that year. We produced over 1000 frames in 1987, the first time that Chris had ever made that many. The "regular" Fats of that model year got chainstay- mounted U-brakes as standard and the Wickeds got the seatstay cantilevers. (Either was optional on both models). The Team Comps were the top of the line and came standard with a mix of Tange, True Temper, and Dillsburg Aeroplane Works chrome-moly tubes and a box-crown fork.