Ok, this may be a dumb question, but... Well, I own 2 Revox A77, a Mark I dated 1969 and a Mark III dated 1972, they're both 2 tracks at 3-3/4 & 7-1/2 IPS and they're both in great shape, so they're basically the same machine. I can record a tape on one and play it back on the other one, swap...