The buttplate states "Herters". Herters was a large mail order (mostly, but they did have several stores) company that provided a lot of sporting equipment under their own name. Everything from Decoys, cookware, tents, camping equipment, books, reloading tools and supplies, guns, and gun parts and accessories to name a small bit of their merchandise.
They imported actions (BSA, Santa Barbara, FN, and others), and had barreled actions an stocks, and also complete rifles.
There are a couple of clues here. First of all, as mentioned, there is no thumb cut-out on the left receiver wall. The recoil pad says "Made in Belgium", and the "R" prefix on the serial number may be a model designation for this 98 Mauser action. I do know there was a "J" prefix model, but I do not have an old Herter's catalog handy.
The Calibre stamp, "7x57" is a bit uneven, and that might point to a custom Gunsmith making up this rifle. Herters did supply lots of stocks, including Mannlicher types.
Back in the 60's I bought a barreled .243 action from Herters, with a stock, and even a finishing kit. It was an exact copy of the BSA Monarch action. The prices were lower than most everyone else's though. The only thing is that you had to take Herters advertising with a grain of salt, as, according to them, they ALWAYS had the best of everything. Today, this would be known as somewhere toward the B.S. side, but those catalogs sure were fun to read.
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