Re:
As I said in your post in the --> 1997 » Retro MTB Chat section, it seems that your frame is likely be a 1999 Caldera. The only other options with those Dropouts and that Cable routing are the 1998 and 1999 Explosif, and rather oddly, a 1999 Lava Dome that also had the superior New (Dew) Drop "K" Investment Cast Dropouts - but that seems less likely now after seeing the colour underneath.
These Specifications are from the 1999 Technical Information, and could determine what your frame is, but it will be tricky to measure. After studying the dimensions, I think that you will only be able to eliminate the Explosif by measuring the Down Tube, then the Lava Dome by measuring the Stays, and then only be sure after that by weighing the frame.
EXPLOSIF
Constructed of Reynolds 853 tubing.
Tubing dimensions: Top - 31.7 x .8/.5/.8t, Down - 34.9 x .9/.6/.9t, Seat - 28.6 x 1.2-.6-.9t, Seat Stays - 18-16.5 x .7t, Chain Stays - 22.2-16.5 x .9/.6t.
Custom drawn, oversized stays with Kona "New Drop" investment cast dropouts.
Made for 27.0mm seat post, 28.6mm front derailleur, 68/110 bottom bracket, & 1-1/8" headset.
Available as frame only, 4.2 lbs (18").
CALDERA
Main frame constructed of seamless double butted tubing.
Tubing dimensions: Top - 31.8 x .9/.6/.9t, Down - 31.8 x 1.0/.7/1.0t, Seat - 28.6 x 1.2-.6-.9t, Seat Stays - 18-16.5 x .7t, Chain stays - 22.2-16.5 x .9t.
Made for 27.0mm seat post, 28.6mm front derailleur, 68/110 bottom bracket, & 1-1/8" headset.
Custom drawn, oversized stays with Kona "New Drop" investment cast dropouts.
Available as frame only, 4.6 lbs (18").
LAVA DOME
Seamless double butted tubing.
Tubing dimensions: Top - 31.8 x 0.9/0.6/0.9t, Down - 31.8 x 0.9/0.6/0.9t, Seat - 29.8-28.6 x 1.3-0.7-0.9t, Seat stays - 19 x 0.7t, Chain stays - 22 x .9t.
Made for 27.0mm seat post, 28.6mm front derailleur, 68/110 bottom bracket, & 1-1/8" headset.
4.6 lbs (18").
Pip