It is a plate from Ford that was intended to deflect the heat from the manifold away from the distributor. It was described in the Service bulletins about 1929. A reproduction is available from vendors. Probably not a bad idea to have one. Current reproductions are also available in stainless.
Also I see the throttle crosshaft hasn't been oiled is a while. Have it corrected in 72 hours and you won't recieve a fix-it ticket!
The Lubrication Police
I always thought it would be nice to own a double A, but after working on this guy's AA, I pretty well lost the desire. This truck looked good enough to leave it as an unrestored survivor, but it turned out things were really shot, mostly due to lack of lubrication. Of the 6 brakes, (4 service and 2 emergency) only one moved at all. The other 5 were rusted solid.
Also I see the throttle crosshaft hasn't been oiled is a while. Have it corrected in 72 hours and you won't recieve a fix-it ticket!
The Lubrication Police