Outside of introducing new models NRB-ST-SST etc I often noticed Bryston quietly improves on the current models with revisions. For example the late model ST’s and the preamps had different (improved) connectors on the input and output boards, even the top plate is different on the 3B; only obvious when comparing images.
Also going by the schematics the 3BST has the capacitors at 10,000/63v but the photo surely shows 12,000/63v, (a revision or were all the 3BST’s the same?).
I remember even twenty years ago not being able to use cables given to me by another Bryton user, we both had the .5 preamp but mine being an earlier version by a few months could not accommodate the RCA connectors as the hole surrounding the jacks were smaller.
For some I believe this curiosity is all apart of the hobby outside of the most important thing, listening to music.