"Is it worth investing a whole box of ammo?"

To me it would be. I love to shoot anything. And I have a coupla' 25 acp's that are fun for me & the kids to shoot.

Back in the day, only 25's and Derrengers were common "hideout" guns. That was a time before pocket pistols could be had in any caliber but "small". Your's is one of many import (probably pre 68 gun control act) pistols that could be had cheap and fast.

I think they're cool little guns, shoot it with FMJ ammo and it may do just fine.

GF