Here's a trick I dreamed up. Somebody else posted a while back asking how to make sure the switch leaf contacts the L shaped contact on the 510 post squarely.
Before taking it apart, lay the P67 on its back, and find a combination of stacked coins, nickels, pennies, dimes, or whatever (I don't remember the combination I used) that just fit between the back wall of the
mod and the L shaped contact. Remember the combination of coins you came up with, and when you reassemble, use the same ones, when you tighten up the
threaded nipple.
I do the same thing when I remove and replace the negative battery spring, because I'm .... about getting the plate nice and square, not that it really matters. It just bugs me when it's crooked.