Mauser Rimfire 4150019 M-15 22rd 22 LR Black Polymer
https://www.tandktactical.com/shop/713440971020-mauser-rimfire-4150019-m-15-22rd-22-lr-black-polymer-28782
https://www.tandktactical.com/web/image/product.template/28782/image_1920?unique=f2ded5c
This replacement or spare magazine is compatible with your Mauser M-15.
