This part has 1/2" crown on top left to right, which should be easy to form with a disk sander. There is no crown front to back, same thickness at front, middle and back. If you are making one by hand, form the top contour so the wood with the felt top pad will fit fairly snug in the space allowed.

Thanks to Dave Godwin for the dimensions.
Someone's comment on the material was "Appears to be Oak", but I have reason to believe that all original wood for the MGA was more likely Ash.