I have three massive 40" x 24" hinged chests each weighing over 45 pounds. The top hinged lid and fixed bottom are made from 3/4" thick plywood with dado edges for the 3/4" thick wood plank sidewalls. Each case has a outer glossy finish, hinges, latch, and metal sliders on the bottom (one with steel ball bearings). Research indicates that these were made by a WWII veteran to store linens. Darkened 1955 newspapers were used as packaging around some items, thus I think they were likely made in the 1945 to 1955 time frame.
I know the actual dimensions of wood products have gradually decreased in size over time but was wondering if there was a general time frame when 3/4" plywood was decreased in thickness. Perhaps they might be made from a special grade of plywood that retained the 3/4" actual thickness verses regular construction plywood.