I'd agree. I have two original 5-round Remington 521 mags in my hand right now, waiting for a hand-off to BrowningGuy, and I can easily compare them to the pics.open mag looks like it's for a Remington 500 series bolt action 511,513,521
The one in the bag looks like a older Marlin and the one without a bag looks like a current Savage mag.
open mag looks like it's for a Remington 500 series bolt action 511,513,521