Oh Purple (sigh). The band Judas Priest took their name from the saying, which is a non-blasphemous way of exclaiming 'Jesus Christ'. Exactly the same way that Irish people say 'Feck', as a polite way of saying the F word.
Another episode shows Hawkeye and BJ visiting some new nurses in their tent. One of the Nurses is reading the book "Jaws" which wasn't published until the early 1970s
Other examples of modern props were episodes where the camp is watching movies. The projector is a more modern Bell & Howell with a fiberglass case. This projector was made in the 60's & 70's.
Another time-warp oopsie: In the episode where Radar is alleged to have fathered a Korean woman's baby, Col. Henry Blake utters, "Oh, Judas Priest, what now?" The rock group Judas Priest wasn't formed until 1969.