I picked up this mystery trek at the bicycle co-op last night. The previous owner not only removed the trek decals, but beat the hell out of the paint and put some random stickers on the frame. He also had what I assume was his name on the top tube in ugly black plain font. I removed most of the stickers but some of his name is still left.

Hopefully from the information below someone could clue me into the model and what tubing was used.

Anyway, as you can see from the photo's it has Shimano 600 brakes, levers, hubs, front and rear derailuers, Sachs shifters and 7 speed freewheel, a sugino crank with 110 BCD (weird huh?). The tires and sakae pedals were from my spare parts bin but the Selle Italia flyte saddle is original. I'm taking the clips off as they're too small for my feet. The seatpost is 27.2 and the bars are Cinelli's but I'm not sure what make the stem is.

What strikes me as odd is the fact that the front and rear rim don't match but the hubs do. Also, there are signs of wear like chain slap on the the right chainstay but the freewheel looks almost unworn. The only thing I can think of is the rear wheel was lost or destroyed and the original owner had a new one built up but with a Mavic G 40 rim instead of the original Saturae C 20. The fact that the front hub was in severe need of an overhaul and the cones were pitted while the rear spins wonderfully confirms my suspicion. Also, the non-drive side spokes are tied and soldered which is even stranger to me.

Not only that but there are 2 lockrings on the bottom bracket. Is this a sachs bottom bracket or maybe an early cartridge version?

So does anyone know what model this is? Also, is it 531?

I plan on keeping the bike original aside from the tires, a new paint job in the future may be possible.