Had a look at some of the picture's in Geddy's book, obviously not many close up shots of the backs of the headstocks and rarely shot square on but you can see notches on at least one of the 50s Ps and a '63 Jazz quite clearly, treble or bass side, and also evident on quite a few Reverb listings of original tuners using google search, and they vary in how pronounced they are, and often visible from the back but barely evident on the hidden front face which suggests to me the tools worked loose during the stamping runs so didn't always make properly square contact