According to the later manual Type G switched from UHF (131-012) to BNC (131-277) at S/N 9480. No idea in which year that was.
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On Thu, Oct 25, 2018 at 08:17 PM, Dave Wise wrote:
I don't know the G serial number at which Tek switched from UHF to BNC*, but
the 1962 catalog shows UHF while 1963 is BNC**. I think I have a newer manual
at home, I'll try to remember to look.
There was a mod kit for converting instruments in the field. I have at least
one modded scope and plugin. Yours too, most likely, as Tek would not have
sold instruments with such an obvious bodge.
* For what it's worth, the 535A mainframe switched at 31260.
** Some old models were not updated.