12" x 6" and embossed.  I did not take this off a machine so I cannot attest what its true purpose is/was.   Has soot/dirt on it from wherever it was used but generally great shape.  Cast Iron/steel (magnetic).  Pricing as if it is real but since I did not take it off the device, please look at pics.   Weighs 5-6 pounds.    One poster wrote in and said he thought it was from a lathe.