Ive seen that on a great many barrels for 1892 and 1894’s but not all.  Ive always thought it could be the result of a Rockwell hardness test on barrels sampled during production.  Or some sort of mark indicating some task was completed in the barrels production, an internal mark, not a necessarily a subcontractors mark.  Dont know.  

Mike Hunter said

Once the threads were cut, Winchester “timed” the barrels using a gage. The bottom of the barrels were marked for all follow-on machining operations.

That is also why you don’t see that mark on barrels with the mag tube relief cut (73,76 86 etc) the mark gets machined away.

 

After going through all the photo I have on the 1892 and 1894 barrels, it appears the punch mark will be seen on octagon barrels, round barrel rifles sometimes–depending on the depth of the relief cut for the magazine tube, and not on carbines because of the deeper relief cut for the mag tube.  Nor have I found one yet with punch marks on TD barrels whether octagon or round.  

Have noticed too that the punch mark is not always in the same location with regards to the proximity of the threads or end of the chamber or proximity to the receiver when the barrel is threaded. 

Again, thanks Mike for the comments.