Okay so according to Classic Air the original components ( compressor, clutch, filter drier and hoses ) were rebuilt to be compatible for BOTH R134a and R12.

The resto shop said they used 134a to charge system (but see no difference in the charging valves/ports).

If I wanted to go back to R12 then Classic Air would have to re-restore compressor and drier at the least...

Don't know of anyone that has a sniffer to detect R12 vs R134a.
Any obvious ways to tell to confirm?