Apparently the wood grips are correct. The only thing the seller should have shown is the matching frame number marked on the bottom behind the mag well.

Info sourced from Springfield Armory Museum - Collection Record,


Notes: "One of the rarest Inglis-Browning pistols is the lightweight experimental. A run of approximately 50 frames (it is now believed only 6 were fully assembled) were made of an aluminium alloy. These usually bear special frame numbers on the bottom of the frame behind magazine well. They were made up into guns using regular production steel parts but the slides were 'dished out' on both sides and on top to remove as much excess weight as possible. They represent an attempt to combine acceptable durability and reliability with the considerably decreased weight desireable in an air force survival weapon. Their grips were made of flat, checkered wood which was lighter than the normal issue plastic. Numerous variations of the dishing of the slide and the checkering of the grips have been observed.
The project was not considered successful as the lightweight alloy frames proved incapable of withstanding repeated firing. Very few of these pistols are still in existence." - R. Blake Stevens