Stamped on the back: 

Hand Crafted from Ceiling Tin, Olde Good Things, Vintage Antique Tin Mirror, "The Place of the Architecturologists" with addresses for NYC and Scranton, PA

Measures 16-1/2" wide by 23" high and 3/4" thick overall.  Mirror is 7-1/2" by 13-1/2".   

Has hanging hardware.

Some rust and wear