Hi
I wanted to list my regs to facilitate servicing and I found out that some have serial numbers and some haven't.
-All my Apeks have them:
.the 4 xtx sets have the first and second with the same number,
the 2 ds4 have number.
-the Scubapro:
.the 2 mk20 have number,
.some mk2 have, some don't...