Looks like mid 50's. I see a lot of "C" service rigs. There is M-44, Brinkman V-88 & V-86, W-44 Mary Braun, Wearl(y?), and Madison Brass Work trailer - I wonder if that was my dad's friend from WWII Joe Maltba he was from Mendota, Wisconsin he ran "F" hydro. Second row left, looks like - Racing Hydroplane, James Walh(X?), Lima ?