For the Mossberg Loc-Box to work, the shotgun needs:
1) a hole at the end of the barrel;
2) a hole on the side of the receiver where the spent shell is ejected, such as that found on the Remington 870 and Mossberg 500, this does not include the Ithaca 37, which has no side-hole;
3) be physically small enough to actually fit into the receiver portion of the Loc-Box.
You might be able to mickey-mouse the thing to fit a single-shot break-action, but that is not what it is designed for.