Dorn is a German company who made a number of meters over the years. They made the Prix (Prize in the USA) from 1939 on into the 1960s. This particular one is a late model because it's calibrated in ASA and DIN. Earlier models would be in Scheiner and DIN or maybe just DIN alone. The first model also had a hinged plastic cover that folded over to shield the photocell and meter face. My model has an accessory leather case to protect it.

It's another small meter, about the same size as maybe even the same works as the Dornlei. The meter pivot is mounted in the corner so the needle has a broad sweep. The pointer is a plate, gold with red lettering, that's mounted in the opposite corner and also sweeps. I have not seen another meter that is configured like this.

To use it, first you set the film speed on the pivoting plate. There's a little nub at the bottom (not visible in this photo) that's part of the plate that's below the top plate. You push the nub until your ASA speed shows up in the center window. I have this one set to ASA 100. (You could also set it by DIN using the scale on the bottom of the window).

Then you point the meter at your subject, see where the needle is, and you turn the pointer plate so that the center is lined up with the meter needle. In this case, the indicator would be ƒ/8 at about 1/125th second, or any other indicated pair.

My meter isn't working and I doubt I'll try to open it. I get the impression it's staked to keep it from being opened by people like me.

Bought it on eBay for $16, with case, box and instructions in German. Also came with a little diffuser for incident reading. That's a piece that's easily lost, so I was pleased to see it's still there.