I was trying to find out what this ammo is and was told it might be 8mm Nambu.  I don’t have a reason to keep it and I’m thinking of listing it for sale if it’s worthwhile. I have 30 rounds.

 

Here is a photo of 3 cartridges, the “Nambu” is in the center without a headstamp, between a 30 Mauser and a 7.62x25 Tokarev.

 

Thanks for the help!

Looks like it could be 8mm Nambu. Here is a measurement for one of mine.