Recently I  examined 2 loose Krag barrels.  Both were stamped with rather large & somewhat unevenly spaced numbers on the face of the barrel at the chamber end - one marked 75.5 and the other 75.6.  These numbers would be covered & not visible when the barrel is installed in a receiver. Does anyone have an idea as to what these numbers mean?   Incidentally, both appeared to be original carbine barrels.

I checked my take off barrel and it has several marks. A sideways "V" centered on a "C",  "J", small "20", and what could be a bomb (fairly small) as seen on 1917 Enfields and others. The marks were probably important 115 years ago, signifying the completed steps in the machining process.
This barrel came off a near 400,000 number receiver with 1898 on the receiver.

Many thanks to all who responded -