Fwiw the pharmacist's recommendation was to not bother checking and just get a booster. She said it was a problem for lots of areas in the 70s and 80s

I was born in the late 80s in a rural area. Got the test and had no immunity to measles and mumps. The pharmacist who gave me a booster shot said rural areas in the 70s and 80s tended not to refrigerate the vaccine correctly making it ineffective