Clyde McCoy was a big-band Trumpet Player in the 60s... not a great musician, but one famous for getting a muted ''wah wah'' sound. This led to Vox trying to approximate this muted trumpet sound in a pedal... hence the Vox ''Clyde McCoy'' wah wah circa 1967.
Jimi Hendrix and Eric Clapton used a Vox ''Clyde McCoy'' model wah wah. Photos taken during the recording of ''Electric Ladyland'' document Jimis as being the ''signature'' model, featuring Clyde McCoys name written out script style on the bottomplate.
The other type of Clyde McCoy was the ''picture'' version, which had Clydes photo on the bottomplate. The ''signature'' model, with its great sounding ''halo'' inductor, is what the Fulltone CLYDE is modelled after.