I still think that they did mark them, but on the stub somewhere near the P proof.  I had some pics, can't find my way into what I've already uploaded to this site anymore.  The single starred barrel I have is very consistent and tight, like .299 bore, .307 groove diameter.  However, what wear and tear has happened over the last 100+ years means we'll find other barrels, starred like mine, with all sorts of measurements.  I would think that if they measured them, they marked them.  Mallory and others say they came with a card and weren't marked.  You just know some guys would be selling their old barrels or out of spec barrels along with the card.