A very nice donation for sure and I'm sure your Post was happy to have it for display . . . but . . I agree on the amount for the receipt of the donation. The IRS now requires that paperwork be submitted in regards to donations. IMHO, a photograph of the rifle should be furnished to the widow (perhaps one was?) and a receipt reflecting the true value of the donated item furnished to her. If you can buy one as nice as this one looks for $500 . . . I'll put in a standing order for 100 of them.
In my community, donations such as this have been made to the Post over the years by well intentioned folks. Unfortunately, once donated, many of them have "walked out the back door". This hasn't happened just once but many times. It has also happened with our local Historical Society as well. I have collected for over 50 years. Yes, I have thought about it and after seeing what I have in regards to folks making donations like this, I have taken care of it with explicit instructions as to how any items remaining in my collection are to be liquidated. My wife and I don't have children so there is no one to "pass' them on to. For that reason, they will be liquidated at "fair" market prices and then the $$ will be donated to charitable organizations which will help others.
Again . . . . I think it was great that she donated to your Post and tht you have it on display . . you obviously have taken care to protect it in a beautiful display case . . . . and hopefully it will remain there for years to come. I just think you've opened yourselves up to some possible criticism by those in your community and organization in regards to the $ amount that you acknowledged - which in return, could come back to bite you later on.
If a pair of '51 Navies were good enough for Billy Hickok, then a single Navy on my right hip is good enough for me . . . besides . . . I'm probably only half as good as he was anyways. Hiram's Rangers Badge #63