British Museum EA5517

Unfortunately, I have not found any good photos of this one. There is a drawing and a poor photo in the one scholarly article on palettes, from 1932 (S.R.K. Glanville, Palettes in the British Museum, Part 1. The title seems to have been a bit ambitious: as far as I know, Glanville never got around to Part 2).  This palette has a  somewhat rare construction technique, though one in the Metropolitan Museum of Art (#10.176.62) looks to be built using the same technique. Instead of the usual method of drilling/chiselling/carving out the pen  cavity and ramp, the worker cut the cavity and ramp with a saw. In brief, a palette-sized piece of wood was ripped into three pieces. The bulk of the body is the central piece, from which the cavity and slot were cut with a saw, and where the inkwells were carved. After that cut was made, the side pieces were glued on to enclose the pen slot and ramp.
Scroll down for some photos that MIGHT clarify things a bit. 
This palette is available in cherry, walnut, and maple.