Originally Posted by
USAZorro
Those decals don't look like 80's to me - not 85, at least. Possibly replacements? Also seriously doubt that's an SBDU frame. Definitely a nice bike that likely has a cool history - one that would justify the required sleuthing to get to the bottom of.
I totally agree it's not an SBDU. They would never have allowed something to leave the shop without the "SB" S/N traceability. I have found head tube decals, but none in this dimension, and none that are circular.