The ammunition is 8x57 Mauser (actually 7.92x57). 326 rounds of it appears to be Romanian manufactured, from what I can find on the web. Both the case and bullet react to a magnet, so I'm guessing steel for both, except that the bullet seems to be copper washed. The cases are lacquered, and there is a red seal on the case mouths and primers. Research seems to indicate that these are Berdan primed. IT LOOKS A LOT LIKE THIS STUFF, but I am not sure about the bullet weight.
25 rounds of it is from a different lot and manufacturer. It is steel jacketed, loaded on five 5-round stripper clips, wrapped in a sort of brown cloth bandolier.
Here is a picture of a sample next to a .308 168 grain match cartridge.

Here's a closeup of the bullet, next to a 168 grain Matchking, so it is bigger than a 168, and certainly bigger than the 150 grain bullet in the above linked example. Maybe it's a 180 or 196 grain?

Here is the headstamp. "22" indicates Romania, and "75" is the year of manufacture:

It is currently loose-packed in a cardboard box.
PRICE: $175.00 (Does Not Include Steel Ammo Can)

I don't know anything about Mauser rifles or the ammo, but this ammunition strikes me as inexpensive plinking ammo.....or maybe "Dawn of the Dead" ammo....whatever. Just know that if you buy this, you'll be helping to support a really sweet (and very cool) missionary couple - so the price is what it is.
Thanks for reading this. PM me if interested.
Edited to update description and amount available.