AC50 mark 2 Slider Boards
Late 1964 to 1968
1) The very earliest boards had two "extrusions" at front. These abutted against the baffle when the board was fully inside the box. Known from serial numbers 1338, 1354 and 1393.
The main rectangular section of the board, made of birch ply (3/8" thick), measures 20" x 9". The "extrusions" are 1" wide and extend from the fore-edge by 5/8". The cutaways at the front corners are 7/8" square.
The four holes for the chassis screws are 3/8" diameter each.
Serial number 1338.
2) Rectangular boards. These rested against the upright runners for the baffle, leaving a gap between the baffle and the front edge of the board. Earliest known example, serial number 1411.
As above, construction is of 3/8" thick birch ply. The board measures 20" x 9".
Serial number 1411.
Serial number 1578. Its board, also rectangular, makes no contract with the baffle, abutting against the upright wooden runners at front.
3) Two cutaways at the front of the board to allow the front edge to slide past the upright runners at front and rest against the baffle. Earliest known example, serial number 1723.
Construction is of 3/8" thick birch ply. The board measures 20" x 9 5/8". Cutaways at the front corners are 7/8" square.
Serial number 1723.