Thanks, just as I suspected....someone "more learned" than I told me that the A stood for made in America and the C was for made in Canada.
More specifically what the problem is, we have a Mics DR 4.1, the NAM with the C died, I swapped it out with a spare A we had, it basically works but I have a DID that used to go to a mailbox, now it goes straight to the afterhours CCR all the time. No switch programming was changed and it took the restore discs ok.
Ideas?
I suspect we are going to the C NAM repaired.
I was really impressed that the backup discs restored recordings, not just structure.