At LaPlaca WoodWorks We try to build our reproduction pieces using traditional materials, so instead of using plywood for the back of the case, we use wide secondary boards instead. For this chest the back boards are 1/2" thick Poplar ship lapped boards with a vee grooved edge.
At the router table we use a vee router bit to profile the edge of the board
After the edges are Vee grooved we next need to cut the dado for the ship lapping, the dado is 1/4" x 1/2" cut on alternating sides of the board..
Next the edge of the dado needs to be profiled with the vee groove bit, this is done on the router table, after resetting the fence..
The chests with the vee grooved ship lapped back boards installed..