Without having the history of the car, there is no way to know if it is 134 without connecting a Refrigerant Identifier. There are so many Yahoo's out there putting everything under the Sun in cars these days, that there is just no way of knowing.

The best way is to charge by weight, beginning with 70% of the specified R12 weight in 134 into an empty, evacuated system. Failing that, with 134, shoot for a high side of about 2.2 times ambient temp with engine at a fast idle, a/c turned on wide open and a supplemental fan blowing at the condensor.

Hope this helps,