I keep scooping up these antique stencil wheels whenever I come across them  as I think they're just fantastic things. This is a very early one, with 1868 and 1871 patent dates (stamped on the face not once but twice) as well as a stamp for Allen Bros. Boston, MA, who would have been the distributor. In the case of this one--which is in very good shape, with a nice warm, mellow patina to the brass on the face --I love the back side as much as the front, which shows pretty amazing greening.

Completely useable should one want to put it to work again.  There were a few different sizes and variations of these made; this is the largest I believe, including all the letters and numbers as well as handy extras (lbs, yds, $, etc.) Held together at the center with a turned wooden handle, the arm on top rotates easily around the disc, with two windows for framing the letter or number to the be used. 

14 1/8" across at arm; the disk itself measures 13 1/8" across. Very good condition, with a minor bends and dings, a little blackening to the brass here and there, mostly on the arm, and what looks like an old hairline crack to the surface wooden knob. Great hung on the wall from the arm or from a letter with the handle hanging down.