Some railroads sold builders plates and number plates. A friend has a GTW builder's plate that he bought on eBay and it came with the original GTW receipt for $25.00! The PRR sold builders plates and keystone plates. Other railroads scrapped the plates to keep fans from going through the yards and dead lines.
The IC sold whistles and probably other items as well. The JiTong railway in China had a selection of builders plates, etc. for sale that they had set up in the company cafeteria in Daban. Of course, employees were selling stuff on the side as well. We had a bunch that followed us in a van for 50 miles, laying their wares out on the ground whenever we stopped for a photo.
The law in most states protects good faith buyers. Since the 481 plate is being sold by a reputable seller, the buyer will have title to it, even if the railroad were to claim it as stolen property.
If you find your property at a pawn shop and the shop has followed the rules and obtained ID from the seller, you will have to buy your stuff back from the pawn shop as they are considered to be a good faith purchaser. I had to buy a $1,600 drone back from a pawn shop that had purchased it from the thief for $400. Cost me $400. And this was with the police detective who had located it present. Aggravating but that's the way it is.
Michael Allen