It's mind boggling to think about the tremendous amount of objects and history in the vaults of museum that most have never seen before, because there is simply not enough room to display it.
When I'm bored, in the shower, or just day dreaming I sometimes like to think about what it'd be like if I was a multi-millionaire or billionaire.
One thing I imsgine myself doing is giving giant donations to museums with the only request that they let me wander around various warehouses and storage areas.
I like history and old stuff, and it just boggles the mind what they must have back there. Especially when I read articles about someone "rediscovering" some old or obscure item because it wasnt catalogued when it was put into storage, or the record was lost.
Visiting Zurich's design museum a few years ago I had that experience -- just showed up at the right time, and since there was no one else on the tour, I got the full warehouse tour (for free!). It was amazing - sometimes you just get lucky ;)
I think if you ask nicely they might let you anyway.
Speaking of museums and archiving, currently there are a lot of archive materials that cannot be accessed or even digitised because of COVID and thus cannot be viewed by the public. Its obviously not a priority but it is a little worrying.
