I was partly wrong. Tek retooled the front panel for BNC, but not until 1967. From 1963 through 1966, they used the UHF front panel with a square-flange BNC jack and plastic trim covering the annular gap. The letter-series plugins built this way are CA, D, G, and L. Others like the K were retooled immediately, if the catalogs are right.
I have plugins of each construction. One of my scopes, a 545, was definitely field-modded, since it was built in the 1950's. It doesn't have the trim and it looks a bit awkward without it.
Beaverton 535A switched to BNC at 31260, but that doesn't tell us anything about Guernsey.
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of cmjones01 <chris@...>
Sent: Thursday, October 25, 2018 1:27 PM
Subject: Re: [TekScopes] Type G plugin versions
On Thu, Oct 25, 2018 at 12:44 PM, Albert Otten wrote:
According to the later manual Type G switched from UHF (131-012) to BNCMy 535A and G are Guernsey-built. The 535A is s/n 101936, and the G is s/n 101127. They both have BNCs which look like they were factory-fitted, though they are of the special Tek type with enlarged flanges to fit the UHF connector hole.