Opinion on barrel blemish

Good morning, a non bullseye question please. The backstory is I inherited 10 collector grade Lugers from my dad. I'm consigning them with a guy that travels the gun shows, lists them online, etc. He sold one, and the buyer call him about a spot of blemish on the underside of the barrel. We didn't notice this before. The first comment from the buyer is "It's been reblued, it's not original."  His friend is interested in another of the Lugers and it has a similar spot.  What do you think it is?  All these Lugers look original and honest. My dad put a lot of time and effort and money into these guns and I really don't think any one of them has been messed with.
thanks for looking,
Kurt
ps anyone interested in Lugers?

In anything but the wartime Lugers, they were usually rust blued.  This means they were polished only just like the picture.  Also, the rust bluing process precluded color on the internal surfaces.  So they were left “in the white” and with machining marks.  So if your Lugers are in the White internally they are likely original blue.  

The mark/blemish is a mystery.  Perhaps a touch up?

In addition, the serial number and proof mark does not look flattened or rounded out, which frequently happens when polished.

Possble reaction Friday from contact during storage?

I have been involved with restoring collector type pistols since the 1960s. After I retired from High Standard, I have trained 4 of the HS gunsmiths in restorations. Today at HS, we (including me -out of retirement)  also restore ALL types of firearms. Your Luger is NOT reblued. In our Interarms Dept, we manufacture the "American Eagle" Luger. We also restore Lugers on a regular basis. I would bet that the buyer might be asking for some type of a price concession ???- Alan Aronstein

alaronstein wrote:I would bet that the buyer might be asking for some type of a price concession ???- Alan Aronstein

+1
I'd give him his money back and move on.  You will find another buyer.  There are a ton of Luger resources, big group of collectors, I'd get touch with them to get feedback on condition and even pricing suggestions.  You might even find a buyer for the whole collection.

Did you get them professionally appraised?  The reason I asked is a friend was selling his fathers rifle collection (12 rifles) and found out it was worth 5X what he was told it was worth by 2 local experts.  He sold the whole collection together for slightly less than the appraised value.
- Dave