When I was about 8 years old, my 12 year old cousin, (also a 57 chevy fan) explained the difference between a 57 150 and a hardtop in a parking lot. The hardtop doesn't have this metal between the windows like a 2 door sedan. It was pretty easy for me to understand. Awhile back, one of my brother's employees was asking about a 57 Chevy he had seen for sale. It was a special rare model 2 door post car. I explained that it was a sedan, but could be a utility sedan or maybe a Del Ray. Long story, but it turned out to be the basket case that I bought for $35, looted the front seat, quarter stainless and radiator and sold for @ $100. The owner was still convinced that post cars are different than sedans. It's no big deal, but I've never seen any reference to post cars in any GM literature or even parts catalogs. I consider it bench racing slang among the cool kids. Cousin Ron still has the sedan he bought about 4 years later and I still have the hardtop that I got 8 years later.