1993 Diamond Back Apex, frame and fork, 1 1/8 inch threaded headset means that if you wanted to, any vintage threadless 1 1/8 suspension fork will work. Top tube cable routing; good paint; NORBA era geometry; $100. Add $15 if you want a 1 1/8" threaded fork.
This is the frame and fork in the attached photo; note THAT THIS IS NOT A COMPLETE BIKE. It's a frame and a fork and a headset.
Frame and fork only; the parts shown in the photos do not come with the frame and fork. Only the headset is included.
If you need parts for building this bike (or for any other bike), I have a weird and obsessive interest in vintage unsuspended mountain bikes, and may have extra goodies from my personal stash that I'd sell for your project. Feel free to ask if you need parts, wheels, and so on.