Never have seen an 1891 scrubbed, let alone so crudely, but way fonder of the 1909's than 1891's. An 1891 is considered an antique firearm with antique metallurgy for firing premodern gunpowder. Also, it seems like an odd thing to do when it still clearly states Mauser Modelo Agentine 1891 on the side of the receiver. Maybe it is just internet nonsense.
There was an estimated 125 million K98's manufactured by many countries. Most German manufactured K98's have the numbers 7.9 , 7.91, 7.1, or 7.2 stamped on the barrel shank, where the barrel screws into the receiver, these numbers designate bore size or caliber. Also, most K98 type rifles have a disc on the stock that indicates the caliber.
You must be one lucky guy. I've seen upwards of twenty model 91s, and all of them had the crest ground off. Including the one that I actually own. The bit about the Argies enacting a law requiring the removal of the national crest from firearms before export is pretty well established. For instance, look at this overview published by some guys who know a thing or two about rifles:
"Collectors in the U.S., though, often find the national crest ground off of Argentine 1891 Mausers. This was done in the aftermath of the Chaco War of 1935, which pitted Bolivia and Paraguay against one another in a vicious albeit brief struggle for control of South America’s resource-rich Chaco Boreal. Argentina provided Paraguay with a large number of Model 1891 Mausers during the conflict in a move that jeopardized its relationship with Bolivia. The presence of unground national crests made it impossible to deny Argentina’s direct support for Paraguay, so after the war Argentina instituted a law requiring the removal of the national crest from any gun leaving the country. Although the government in Buenos Aires later dropped this requirement, by then most of the Argentine 1891 Mausers had been ground, and this accounts for why it is rare to find one with the crest intact. "
https://www.shootingillustrated.com/content/the-1891-argentine-mauser-a-history/The requirement that firearms imported into the US after 1968 are required to have the caliber permanently and indelibly marked is well known and is documented at Wikipedia, among other places.
As for the caliber stamps on Mausers, some have them, others do not. I'm not a Mauser maven, and I don't know whether those stamps were placed there during manufacturing, during export, or during import. Do not assume that any engraved mark on an old firearm was put there on manufacture.
