Questions about a proofmark on a K98

At the big National Gun Day Show here in Louisville, Kentucky I picked up a byf code, 1942, K98 Mauser. The gun is mostly mathing, including the receiver, floor plate, barrel band, etc. It comes complete with a vintage, World War II era military sling. The bolt is a mis-match. Overall, the rifle looks to be in relatively untouched condition. It still has the original capture screws present.

My question is in regards to one of the proof marks. The barrel is not numbered. At least not in the typical Nazi fashion. Not that I can see. However, both the barrel and the receiver have a proof mark I have never seen on a wartime K98. It is a "crown over u" marking. The man I bought it from told me that that particular proofmark was East German. He also said that rifle had an interesting history. First manufactured by the Nazis in 1942, it was later re-issued to the East Germans, who probably sold it to the Iraqis. Any of that sound correct? There are no import markings anywhere on the gun that I found.

Above the "crown over u" marking on the barrel there appears to be some type of eagle marking, but it doesn't appear to be Nazi. It looks similar to the Imperial German eagle marking, but I do not think it is. On both the barrel, and in between the "byf" and "42" markings on the receiver, is another marking I cannot quite make out. It appears to be somewhat triagular in design, by that's about all I can see of it.

Any information you can supply me would be most appreaciated. If you're wondering, I paid $650 for the gun. It is serial number 612f.