I did look in the RCA manual, and an old Sylvania CRT manual and it's not listed there.
It's on the chart of the B&K 467 CRT tester and a test adapter is listed at oldradioparts.com for it.
http://www.bkprecision.com/support/d...etup_Chart.pdf
I don't need to know. It's just to satisfy my curiousity.
John