Indeed.
This rifle is an authentic SSZZA4 built from a salvaged receiver, a byf41 marked receiver to be exact. To start, the 2 major categories I put these in are reworks and builds. The reworks seem to be first in the series (in as much as we can tell from the breed- its really speculation, both could potentially be done at the same time, but in our world we need seperation). When they reworked guns, they took the receiver serial number and used it as the weapon serial number. This rifle leads me to believe even more that reworks were early and builds were later. The barrel serial is typical of later SSZZA4 builds - serial placement, SSZZA4 placement, etc - so you know this rifle was meant as a build.
On this rifle, the receiver was reclaimed. Quite a few comments about the ground serial number, and suggestions that it was incorrect or altered to remove a mismatch serial. It actually was - the original serial had to be removed to use the receiver in a build, so it was. I'm not sure why its surprising to some, except for a lack of understanding about the German depot system in general. Things were recycled, more later in the war than early, but nonetheless recycled parts were routinely ground and renumbered. Many K98k parts were evacuated from the Posen depot system ahead of the Russian advance, with many parts ending up in regular production lines as seen at Mauser and Brünn Its one reason collecting reworks is a minefield, work done in 1945 can be duplicated any time since. When viewing reworks, you have to see the whole of the gun and compare fonts, workmanship, blueing. Its all relevant.
Add to that, this sub species of SSZZA4 is rarely found - I haven't gone through my data to see if there are others reported, but surely they exist. The majority of these are built using new components supplied by Gusen production to the SS depots, perhaps for just this program. Notice this rifle also has an "H" front band - not as common, but perfectly correct for SSZZA4 builds and reworks. Even flat buttplate stocks are seen.
The price was good IMO - the pitting on the rear sight base and other part, plus the bad images hurt the final value IMO, but the buyer got a real bolt mismatch SSZZA4 rifle.