I sure dont want to get anyone upset about unique, but here goes my stories.
I was brand new in the hobby and did not know what a Hellsgate bridge looked like. I bought a nice collection that had a large bridge with Lionel track screwed to it. There was a 38 water tank and several nice motorized units.
When I got home and looked up Hellsgate bridge it wasn't close. This bridge was single track, in 3 pieces, and 71 inches long. It had no markings at all.
I took it to a TCA meet thinking someone would know what it was and tell me what it was. Many people did know what it was but they just wouldn't tell me until I sold it to them. I learned a lot about TCA people thst day
It turned out to be a Marklin 1 gauge bridge hand made and hand painted in 1907. It was worth several thousand dollars. I sold it at York to a man from New Jersey who was honest with me and gave me a bunch of information on it.
The other item was a postwar merchandise car that throws out cubes. Supposed to be silver with Blue letters. The night before going to a train show, I was reading in a Greenberg book that there were 12 known that had red letters. First table inside the show had one red letter car in a early postwar set. I didn't hesitate to buy the set just to get that car.