Factory changes of Anti Hums to HB-1 Pick-ups

[Aristocrater]

I sort of remember reading somewhere that some guitars that were originally equipped with Anti Hum pick-ups got upgraded to HB-1s when they went back to the factory for repair work. Are there any tell-tale signs of the factory doing the work? How much larger are the HB-1s than the Anti Hums? Would it be possible to re-install Anti Hums on a guitar that had HB-1s put in it or is the opening now too large? On hollow bodies guitars (those with labels), were any notations made on the label? Thanks in advance for the education.

 

[SFIV1967]

What you refer to as "Anti Hums" are the 60's mini humbuckers. See Hans' book pages 32 and 33 for all details.
Basically the 60's Guild mini humbuckers were, as the name suggests, smaller than the regular sized 70's HB-1 humbuckers.
The easiest visible distinction is that the mini humbuckers had only two height adjustment screws (one on each side) whereas the HB-1 had 3, so you could adjust the tilt as well.
See some info here from our member GAD as well: http://www.gad.net/Blog/2011/11/25/guild-full-sized-hb1-and-sd1-pickup-variations/
And no, the label didn't show which humbucker was used.
Ralf