Welcome, new person.
On behalf of the community of gun folks who inhabit this asylum, let me apologize for the utter failure to inquire where you live and the faulure to offer to be at your doorstep within the next few hours, Blue Book in hand, to help you sort through what may indeed be a treasure trove.
As well as belated condolences. (We are somewhat "challenged" on the social graces at times.
)
While it's most likely your dad's gun cabinet is not holding the last intact box of some rare caliber/configuration, there is still a market out there for older ammo. Once you ID what you have via the headstamps you can check the local on-line trading lists for general prices, then either offer it there or invest the money to set up a table at a local gun show. Most old ammo is sold face-to-face in order to eliminate dealing with the paperwork (not really that bad) and the cost (sometimes more than the ammo is worth) of shipping in compliance with all the hazmat requirements.
Your hubby sounds like a keeper - anybody that suggests long-term storage of ammo for which there are no current firearms is plotting on correcting that situation without disposing of the ammo. He just needs some education in the fine art of sanding and repainting ammo cans as opposed to vac-sealing ammo (which is done for short-term storage/transport through hostile climates).
Post pics of what you cannot figure out. We love solving puzzles.
stay safe.
