I was having red light problems on my'66. Light would sometimes go out if I gave a bootfull but it was getting worse. Almost certainly bad brushes so I checked and tidied up another one. Took the bad one out, the red one, and found it to be different to the rehabed one. Checked a couple of others and found them all the same as the black one. All Bosch but didn't check numbers. Fitted the black one and red light is now working perfectly with a good charge.
I don't know what the hole is you're talking about. The only ones I know are hidden by the brush access band. Do both of yours have the same type of end plate as either of mine or do you have two different ones like me. I think the black one is the more usual type.