Need info and price check on 1906 commercial .30

[Olle]

A customer has asked me to sell his collection of C&R guns, and one of them is a 1906 commercial in .30. I have looked it up, checked the features etc and everything seemed to check out until I flipped the safety. It has the correct "up safety", but the milled area underneath is blued. You can see that it has been milled, but the finish is exactly the same as on the rest of the frame. It has not darkened by age or been touched up, it looks like it has been blued at the same time as the frame. On every other "up safety" Luger I have seen, there has either been a milled area in the white or the text "Gesichert", so this kinda stumped me.

The inside of the frame is in the white just like it should be, and the bluing looks entirely original, so I doubt that it has been reblued. It looks a bit dark in some of the pictures, but the finish is the correct "Luger blue" rust bluing. So what gives? Is it some kind of factory rework, or did some of these come without the bare steel milling?

I would also appreciate your ideas on the value. The pictures should give you a pretty good idea about the condition, the bore has sharp and deep rifling but is a bit dull and has some scattered, shallow pitting, and I assume that the magazine is correct. I'm going to put the guns on Gunbroker so I need to figure out what a reasonable reserve should be, and I'm sure you guys will know exactly what it's worth.