Broken valve plate Speedaire 8YJ20A BY DAYTON

This compressor sayd in the tank "Cast iron series" made in USA. My problem is that I have a broken plate that I supose is Call "valve" in some of the diagrams of other models, but none of them looks like this one.
The size of the square tin plate is about 2 1/2 x 2 1/2 inches, less than 1 1/16 thick and the purpose of the plate is to seal the intake hole when the piston is going up.
If any one knows what I`m talking about and want to help me I will apreciate it.
sonnyduque1958@hotmail.com