Richard Cunningham originally offered the Mantis XCR as a fillet-brazed, all-steel frame in 1983, and then with an aluminum front triangle and a steel rear end beginning in 1984. The idea was to capitalize on the best traits of each material. Sometime around 1989, the elevated chainstay or EC version of the frame was first offered, which solved the dreaded chain-suck problem. The XCR is exceedingly rare and the rarity factor of this bike is perhaps only undone by the fact that from a distance it is virtually indistinguishable from the Sherpa which is a somewhat more common of the early Mantis bikes. The two bikes only differ by the slightly more aggressive geometry of the XCR, 17" chainstays vs. 18" on the Sherpa and a longer standard top tube for a more racy feel.
Special thanks to The Pros Closet
for the information and original photography.