I have one of these SCI marked G22's as well, also a CGL prefix. I got it from a friend of my dad's in Tucson back in 2001 or so.
GLOCK Certified Armorer, GSSF member, NRA Life Member
Currently: 17x2, 17L, 19x2, 20x2, 22, 23x6, 24x2, 34x2, 35+1, AA LE 17-22 on G31 frame, Olympic Arms K9-GL
Have owned: 21, 26, 27, 29, 30, 31, 32, 33, 36