Was the “deaths head” stamp on the stock applied when it was originally “built”? Or, doing the rework?
This former Karabiner 98b (a zero series of only 1,500 pieces, made from materials like DIN-steel that were only to be used in the event of mobilization in threat of war, because less quality) was built in 1932 by the Jewish company Simson, they did not use SS symbols. It was an Reichswehr Ministry order and the SS got this carbine at a later date.
The "death head" was applied to the stock after the rework/conversion was carried out, which was probably done around 7 years after production.
If the carbine match, then the barrel examination report of the SS armorer gives us the date of February 13, 1941, by which this carbine had already been converted. It was likely in service since the formation of this SS Cavalry unit.
I remember the saying that it is usually impossible to find out the unit in which a K98k has served, it's like a lottery win. In this case we know the exact unit, the location, the exact date and much more.
@Loewe
Here is a short excerpt from one of your comments:
in 1932 Simson was in a pickle of situations, and all things considered made the best of a terrible predicament- Arthur had the great fortune of a long life in California, the young Loewe family disappeared I believe, which bodes bad odds...)
Even if it's not important for the actual topic, I still wanted to show you this.
The squadron leaders daughter of the SS unit in which this carbine serial number 268 served, had the great fortune of a long life in California - like Arthur.