Copper Printers Plate

I found this old time copper printers plate at an antique mall. It is a set of nine portraits etched into a copper plate creating a negative which I scanned once as it is and then flipped the scan to show what it would have looked like on the printed page. It is marked “Wisconsin State Senators 1927” with a felt pen on the back so I assumed it was for a page from the Wisconsin 1927 or 1929 Blue Book and that it would be easy to look up the guy’s names since I have those Blue Books. Well I could not match the pictures with any in those Blues Books and with the size of 144 x 180 mm this page plate would have been too large for a Blue Book. This plate also has a 3 mm rim on all four sides with nail holes for mounting. I guess back in the good old days a printer also need some muscle to set these plates which can get to be fairly heavy. Anyhow if anyone here recognizes this plate or may know what book was printed from it please let us know.