Eric,
As I stated before, they are found on Lugers other than the Test Trials pieces.

Are simular marks on any other mags?

Yes. The mark is not a US Ordnance mark. People like to put a flaming bomb mag in a Test AE because they think it needs one, but an unmarked magazine is also proper. The mark is just an inspector's mark and it could be on the wood base of commercial magazines for various commercial Lugers.

Thank You thats a releif.When I bought it from Gramps, it did have a properly marked mag. That had to be 8 years ago. Since then I've lost both my mind and the mag. I didn't want to pay $500 to correct my stupidity. When they were issued we they given 1 or 2 marked mags if you know. You better write a book!

I doubt that the magazines were marked and I do not know how many magazines were purchased. The order was for 1000 Lugers, 200,000 rounds of ammunition and "spare parts". I do not know if extra magazines were included in the spare parts.

I know precious little, if anything, that has not already been written in other books. I doubt that a book that I would write would be of much contribution. I have nearly 200 books in my library, predominantly Luger related but also include other early pistols and revolvers, pickelhauben and German history. I probably have an equal number of magazines and periodicals dating back to the early '60s. My books are in seven different languages. I can read the English ones pretty well, the Swedish and Russian not at all (but some of the pictures are informative), and the others with varying levels of difficulty. So, by and large, my knowledge is derivative, I stand on the shoulders of others before me. My simple contribution is the research I can do with my references and provide the information from them along with the experiences and knowledgeable friends I have been privileged to have for over a half century.

Thank You Ron. Your a Gentleman and a Scholar!