I've got an old Berg Precision 90 piece that has what look like file marks on the inside of the side rails and I'd always assumed that someone had tried modifying it. But I've seen photos of other similar marks on old Bergs for sale on ebay and on here, so I wondered if these fine, regularly spaced grooves were from the manufacturing process. It plays well, with a woodier tone than some of the modern ones.
90 isn't so bad to play, but this was my first mouthpiece, so I'm used to it..
Trying to find info on the approximate eras of the different Bergs I have is difficult - the Precision, the one's with the more rounded end on the shank, the step baffle etc
Theo's mouthpiece museum page is helpful, but gives less info on ebonite Bergs. Perhaps it's just not possible to know with any certainty how old these things are and it's best to stick to playing them