OK, I was wrong about the serial number.
Doug Murray's book on 99 says that the change to the tang safety came in 1960 for the F model.
Interestingly, the .358 was chambered from 1956-68 and from 1977-1980, FAR longer than the .284 (1969-1972) or the .375 (1979-1980).
I knew there was a cartridge missing from the ones mentioned here, but I just couldn't put my finger on it. It was the 7mm-08.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.