While "Standard Gauge" really means that a freight car from anywhere in North America can show up anyplace on the continent, there's still some unusual findings lurking if you study a particular railroad long enough.
Take my pet prototype. I'd never bet on seeing an L&N drop-bottom gondola hauling coal in a Connecticut, or not one, but two 50-foot SFRD reefers in a train in Massachusetts. But I have.
In a previous blog post I mentioned a boxcar that showed up in a photo of an otherwise nondescript CV freight. I've explored several seemingly plausible identities for this car, only to be foiled by one detail or another.
Ted Culotta recently posted his thoughts on this car on his blog:
http://prototopics.blogspot.com/2019/12/marty-mcguirks-mystery-box-car.html
I'm curious to see if anyone comes up with any evidence disputing his findings. And if he's correct, as I think he is, this is not only an unusual car, it's a one-of-a-kind. Just my luck.
Now to figure out how to model it.