I'm not aware of Colt EVER making a 10-round 7.62x39 mag. The standard Colt factory mag is a 20-round .223 mag with a block in it that allows the mag to hold 5 rounds of 7.62x39.
Before you buy, I'd ask a lot of questions, as these may be some funky aftermarket mags.
Ammo FAQ: www.ammo-oracle.com
(Old) Mag FAQ: magfaq.tripod.com