I've also been lucky enough to find postcards of different concept art and models for stadiums that hadn't been built yet at the time. These are some of my favorite postcards as sometimes the final design was a lot different from the finished product.
I was thrilled to get this concept art postcard of my favorite stadium in MLB, my hometown Royals' beautiful Royals Stadium (as it was known back in 1973).
I'll throw in one last card for my pal and die hard St. Louis Cardinals fan Neato Coolville. Busch Memorial Stadium was all kinds of 60's retro cool.
I'll try and post more cards from my collection in the near future.