This may sound like a loaded answer but if it has R12 fittings its likely to be R12 and the same for R134.
Either system should have a decal under the hood saying how much and what type of refrigerant. This even applies to retrofits. Part of the rules for retrofitting is to label the modifications.
And then for the real answer you take it to a real A/C tech who will have a refrigerant identifier which will tell him if anybody lied.
[Edited by stevebfl on 04-12-2001 at 06:22 PM]
Bosch Master, ASE Master, L1
33 years MB technician