via this auctionSN 262175

EVERYTHING SYNTH

Three versions of the Axxe were manufactured, the last two containing orange silkscreening and a slightly modified case. The difference in these later two versions was primarily the mounting of the keyboard. The earliest units of the original version lacked ARP’s innovative “Proportional Pitch Control” pads, but featured a copyright infringing version of a Moog filter that was later discontinued, though no actual lawsuit ever took place."