The main issue I have is whether Mongoose's term "Complex Ferrous Array", or CFA for short, even means Cr-mo, let alone 4138 Cr-mo. The seller of the bike believes that's what CFA means, I'm trying to verify it. It seems to be a Mongoose-only term, nobody else seems to use it.

The thing is, up until 1997 Mongoose claimed that these bikes had Cr-mo frames. For 1997 they changed the description to "CFA" and significantly changed the frame (e.g. went from 1" theadless to 1 1/8 threadless). It seems to me that if it was still a Cr-mo frame they wouldn't have changed the description to this mysterious "CFA" designation. As DannoXYZ says, it is likely that the steel is just hi-tens. Somebody out there will know....