My brother in law found these in the rafters of his garage. There are 12 cartridges in the 22 HP box and the box of 38's is full. Any idea how old these are and if they're collectible?

Probably from the fifties, No warning about children on the boxes,the rem may be earlier...22 collectors want clean boxes, full of original shells .....The 22 box are to worn out and your only hope is to sell the cartridges to a person that needs to fill a box.
As for the 38's sell them or shoot em !

BB