No offence taken Shane - I am actually fairly old 
My 2 cents worth:
Most people who buy on eBay are trying to get a bargain; most people who sell on eBay are trying to make a profit. The scabbard is not an item of national importance - it may be something that the museum would care to add to its collection.
If you had not spotted the item, bought it, taken it home and cleaned it up, researched it, and contacted the museum about it, the museum would never have known that it existed. If they want to make you an offer that gives you a nice profit, then I would say good luck to you.
