Unlike you I am old, but I was not into photography - nor did I appreciate these cameras, in my time. But I have immersed myself into it and have acquired a few to learn about them during their timeline with help from website like this as well as magazines of the time. But since I don't buy and sell as a business, I likely don't look at their "value" as you do except for a few items like the Canon 1VHS that I bought locally strictly because it was too cheap to pass up ($100) to sell or trade. I managed to trade it for a Pentax K 50mm f1.2 lens which to me was a fantastic ROI.
In your business, I would imagine you would evaluate the FE based on cosmetic and functionality and keep track of historical trends - such as completed listings in the auction site. I haven't looked but a fully functional black body Nikon with no scratches likely fetches more then what you paid for your. Interesting that you didn't specify the lens - especially if it is a Nikon brand. That may bring back even more then the body too.