It is an engraved metal printing plate mounted on a wood backing block. The business end/face is either copper (likely*) or steel and attached to the backing block to keep it flat, easier to handle and lie flush with the rest of the type-set page in the press
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You could use it alone or more likely with other blocks assembled to make an entire page of copy for a semi-(?)automated printing press.
Result would likely not be one/few copies but a large number of newspaper/magazine/advertising pages.
My guess of copper is that this would be a hand engraved plate easier to carve in relatively soft metal giving good results with a useful lifespan. If multiple plates were to be made for an advertising campaign, including replacement of damaged ones, it would be much easier to carve.
A steel plate would last longer but that would be decided by the time/cost equation.
See If the plate attracts a magnet &/or is red or silver/grey if scratched/cleaned on the side.
Of course I am often wrong but my opinion is only worth what you paid for it.
Best,
Lee