Judging by the distance between the top tube and the down tube, it looks more like a 55 cm to me.

Klein made lots of different variants of the Quantum bikes. That makes them hard to identify. As far as I know, there's no reliable serial number information available. After looking at the pictures on Diablo Scott's webpage, my guess is that frame is a 93. That's base on the shifter bosses, top tube brake cable guides, the Klein font, and the placement and font of the model name.

Note that you have a square taper spindle which is pressed into the bottom bracket. That will limit your options for a crankset. There aren't many options for replacing the bottom bracket, either. Unless you swap the fork, you'll need to find a nice 1" stem and compatible handlebars. That said, you can put modern equipment on the bike.

I have an 1983 Klein Performance and a 2006 Klein Q-Pro. PM me if I can help.