Hasselblad Film Magazines
12 (M-12) Manual back with peephole
A-12 (I) First A-series back with hinged film tab holder and film ASA/DIN dial.
A-12 (II) Modified A-series with fixed film tab holder and no ASA reminder.
A-12 (III) aka A-12N 1997 A-series back with built-in darkslide holder. Fixed film tab holder, no ASA reminder.
ECC-12 1991 Electronic databus back with film speed and zone system control
E-12 1994 Simplified databus back with just film speed control
Dear Bill,
1994 would be an A12 II which would have a date code matching your body, although sets from new sometimes had date codes that were different.
The model code in black trim (chrome was not supplied with the body) was 30147, in the 1997 catalogue when the the A12N back was introduced and the 501C was still available, it is clearly stated the 501C is supplied with the back that does not have the magazine holder although that was now avaialble.