Nice catch! Sold a number of that same model back in the day.
Preachin' to the choir again, but don't forget the two ground stakes on the far-right end of the chroma board need to be reflowed. That's routine on any CTC-12, 15, 16, 17 and 25. When (not if) one of those grounds lets go, it kills the heaters on the two 6GU7s. That allows beam current in the CRT to avalanche, which ain't good.
You're gonna remove and reinstal the CRT?
Here's a tip that's better to learn now than later: After a CRT replacement, the whole jug will gradually begin to tip backward, creating a larger and larger gap between the mask and the top of the CRT. We learned quickly to
thoroughly tighten the steel band securing the CRT to its 'mounting ears'.