Looks like 134. The R12 had smaller black plastic caps. On yours it looks like the proper 134 lines and accumulator were installed and not just the conversion kit. I did several of the conversion kits back then and the new ports for high and low side just screwed onto the R12 fittings. Yours doesn't have that, so good news is whomever did the work, probably knew what they were doing.
On the home owner DYI kits and some shops, these didn't relabel the work. Reason for this is because the need of the certification. If it was done DIY or uncertified shop, the fear was EPA could come back on the home owner or shop and generate fines. This was because the DIY'er or the shop was not certified. EPA assumption was..., not certified..., you must be incompetent and it was done incorrectly, therefore..., shop deserved to be fined... If done DYI as a purchased conversion kit, by the registered car owner, they didn't really get involved. Wal-Mart and some others, sold the kit for about $35.
Like said above..., the best is to evac the system and replace the oil and refill with refrigerant. Also replace your orifice tube. You would be amazed with how many times a compressor was changed out and yet, not the orifice tube. The tube will get plugged up and if not changed, the AC will not work properly.
Not knowing what's in your area... O'Reillys Auto has the vacuum pump and manifold gauge set you need. You rent and return and the cost is returned to you as long as you return the tools. AutoZone also has same. Not sure what's in your area.
Purchase the small thermometer and place in an AC vent. When done correctly, you should have 55 to 60*F coming out of the vent.