Hello, I was wondering if anyone can help me. I'm helping my aunt go through my late uncle's train collection, and we found a piece that I cannot find anywhere, and I was wondering if anyone could provide some info.

It's an O gauge boxcar, Louisville & Nashville The Dixie Line. I see a model number of 105000. Not looking to sell, I'm just curious as to why I can't find this online or in a Greenberg guide. Any guidance would be much appreciated. Thanks!