Hi winston...
The date info on the Schaller and Müller bridges comes from Brian Bowdren's Guild Pilot ""Bible", The Workingman's Bass...
However, since I wrote that post and while I am STILL waiting for f'king FedEx to deliver it, I have been thinking that I may have misunderstood what he wrote...
Brian wrote that the Schaller roller bridge was the first bridge used on the Pilot line in 1983-'84 and that the Müller bridge, the second and most commonly found on Pilots, was (also) OEM from 1984 - 1994...I took these dates literally, thinking that Guild went FROM Schaller OVER TO Müller exclusively in 1984 - and it seems obvious to me NOW, that Brian probably meant that the Müller bridge was brought in as a "second option" from 1984 and that from then on, a Pilot would get either a Schaller OR a Müller depending on stock, worker preference, model, usw...
So, "my bad" as they say - sorry...

But, in my defence, until this most recent Pilot purchase, none of the dozen or so Pilots I have owned, do own or had my hands on since 1987, had a Schaller - ALL of them were/are equipped with Müllers, with the single exception being my '94 Pro 5...