Wooden ammo crates were being phased out by the late 1950s, and nearly extinct by the mid-1960s, having been replaced by corrugated cardboard. There are several different construction styles of wooden ammo crates. The very early ones were very well made, got cheaper as time went on. Note the jointed corners of the Remington crate vs. the others with simple nailed corners. Your shotshell boxes are from the 1950s and 1960s. The one piece cardboard shotshell boxes began in the late 1930s, and were about the only kind in use from the end of WWII onward. Prior to that, most shotshell boxes were two piece. The oldest wooden shotshell crate I have is a UMC crate for 10 gauge shotshells from around the 1890s. Printing is barely visible.