You might research the bulk of representations to see which was his favored side. If this was a printing plate the image would be inverted. This is not likely to have been the whole plate but was cut from the block for someone's keepsake. It would have been easy to distort the plate with say, a hammer and chisel.
What a great looking find!
I'd have an imprint of it made on a piece of old parchment paper or velum, then frame the two pieces together for posterity.