The seam was a lap joint (scarf joint) on all these. They applied the wrap to the flat plywood before they bent it into a shell.
Up through the 70's the outer ply on wrapped drums was almost always mahogany. The center ply was always poplar and the inner ply was usually mahogany but also varied between mahogany and maple (which wood should we use today Bill?). The white paint helped make them look the same regardless. Around '68 they changed things up, the interiors were clear and always maple (with some exceptions as older shells got used up) and the wrap was applied to the shell after it was bent.
The lap (scarf) joint seam remained until the late 70's when they switched to the 6 ply maple/poplar shells. Those did have the Gretsch style staggered seams.