Hi Juliana! you've got a good number of excellent responses to what I'm sure you were hoping was a simple question! Most of the work I do is helping museums develop operationally sustainable collections. Here's how I usually approach an "oversized" collection.
1) Stop the flow mission-irrelevant objects into the collection: Review, revise, and readopt the Collection Management Policy (if you have one).
2) Figure out what you have: Perform a high-level and eventually an item-level collection assessment. This will help you understand what objects really support the mission of the collection and which do not.
3) Write down what the collection SHOULD contain to be a well-honed mission-delivery tool: Collection Development Plan. This is like a strategic plan for your collection (though there may be professionals who approach this a little bit differently). This is where you decide what to keep, what to deaccession (and disposal options for those deaccessions), and where to focus collecting efforts in the future.
I know this seems like a huge amount of work (and it is!), it will help make solid, defensible decisions that you can transparently justify to the public.
Good luck!
Erin
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Erin Richardson PhD
Founder and Principal
Frank & Glory
Cooperstown NY
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