For what its worth:
The old Oldham front seal I regard as US without the old reflector, its better replaced with a new one like the one Mr Mike supplies with his Retro conversions. Unless of course you incorporate the glass into your own front end extension.
Oldham switches are designed so that a bezel is forced against an impregnated felt washer. Itโs pretty bombproof; I have never known one leak. Stewart Kirby lamps replace these with a rubber O ring.
The cable gland is best filled with silicone as I do on my lamps.
Wise to put a blob under the positive charge screw as well
Later designs have the charging assembly screw penetrate right into the lamp; early designs were a blind hole. Again, I seal with silicone.
The grey lamps were the first to be designed like this, then the black ones followed suit.
If in doubt, test the lamp in a bucket before fitting the electronics.
My avatar is a poor likeness.