How to figure out year of my old Peugeot Triathlon

[moreland01]

I can't remember what year I bought it, but I know it was between 1985 and 1988. The number on the frame is Y712 10960.

All the parts on it are original Shimano. I don't think I ever rode it after 1990. Nothing has been changed but the seat, handlebar tape and pedals. I'm going to attempt to sell it. According to my bike mechanic, the Shimano set is in excellent condition. Picking it up again after all these years, I'm blown away by how light it is. Like a feather. Especially as compared to my ebike

Any idea what it's worth? Will need new tires and a tune-up. It's a size Small. I'd have to figure out how to do a centimeter measurement.

 

[moreland01]

Update: Some research tells me that the date of mfg is Dec 1987.