Bag of 40 factory new REMINGTON unprimed 375 REMINGTON ULTRA MAGNUM (375 RUM) brass cases
Odd numbers of cartridge cases is the result of bulk bagging. Bulk brass is sold in barrels, generally by weight and it is not uncommon for odd number of pieces remain.
Brass case mouths MAY not be perfectly round from the manufacturing process, this can be corrected by running brass through the size die (always recommended) prior to loading. Residue from the annealing process may leave a stain on the case neck that can be removed by tumbling. Annealing involves rapid heating then cooling to impart the shell cases with the proper hardness to securely hold bullets in place and provides flexibility to expand and contract through multiple firings handloaders expect.