The very first photo in the very first post shows the "U" proof stamp with completely abraded edges.
This pistol has been heavily scrubbed and refinished. Which is a serious killer-criterion for a collector.
Nevertheless, it's still probably worth 1K or so, just because it's a C96.
And Jim has made the right comment: see what they are actually selling for. I have recorded sale prices for my guns for years, so I have a fair idea what they might fetch at auction. Bottom-value estimates are recorded in a spread sheet, with a warning to my heirs that if they are offered less, someone is taking advantage of them. In some cases - the Garand, for instance - the prices are now so sky-high and rising, that it is hard to believe what I actually paid.