Photorama was started about 20 years ago by a guy named Sam Vinegar who ran Classic Camera in Grosse Pointe, Michigan.
The original events were akin to swap meets held at a local Millwrights Hall.
He built them up over a period of years. At its peak he was renting large venues with over 100 tables/dealers over a wide geographic area.
This was prior to the digital revolution which decimated Photorama and left it a shadow of itself.
That said, some of the remaining dealers continue to offer decent older gear at fair prices but you will likely have to sort through a lot of chaff to get to the wheat.
And whatever you do, HAGGLE! And have fun! 😀
hth!/ScottGee1