I agree with the above comments. I have been leading our local historical society through a number of professional upgrades. A mission statement is important, but springing from that is the Collections Management Plan, also called the Scope of Collection Statement. What do you collect, how many of each, deacessioning, and much more. Focused on collections of all kinds. This becomes your sword and your shield for accepting or declining donations, as well as purchases and exchanges. It is retrospective in guiding you to correct the exhurberance of the past. The CMP must be approved by the board so all are on board (pun intended, sorry). For iffy donations that the collections committee will probably reject, we ask the donor in advance of the meeting what are his/her desires: toss, keep and sell, return.
If you are removing objects from past acceptances, keep notes. I keep them within the minutes of the coll. committee.
The director loves the collections committee as she can make them the bad guy instead of herself. We are happy to oblige.
And, you can always wave the Coll. Mgmt Plan at a donor stating, “we must follow this plan and according to the plan we can’t take your stuff.”
Finally, deaccessioning is a bit different from just removing something from the property.
Hope this helped.