Same procedure on the Herc J fleet in the 2000's.
Descending though transition a cross check was done with whichever altimeter showing low becoming the master. Usually a comment along the lines of "20 low, mines the master". If the monitoring pilots altimeter was the master then you just called your own heights during an approach. If the flying pilots altimeter was the master then the monitoring pilot would just take 20', or as needed, off their indications.
Worked well and I still make note of it today.