My good friends over at Briarpress helped me identify this, my latest treasure, as:
“a Baltimorian” #10 by J.F.W. Dorman Company. 1885-1904
(Or a “Baltimore” #10 by Baumgarten & Co. 1895-1900 as they are practically identical).
Very helpfully, the post also included these links to some very handy press identification sheets. I am indebted to Oprion for these: