An original R12 system will have simple 1/4" inverted flare fittings. A 134 system will have quick connect fitting adapters that look a little like quick connect fittings like are used on air tools and such.
That said, there is so much bootleg conversion of systems without putting on the correct fittings that the ONLY way you will know what is in the system is to go to an auto a/c shop and have them check it with a refrigerant identifier.
I don't know what your goal is, but if the system is not working and you plan on charging it, and you don't have complete history of the a/c system, you should have it identified. These days ANYTHING could be in the system regardless of the fittings. It's a really pathetic situation.