I found this one in Cambridge MA, just a few miles from Devonshire St. in Boston, where the New England Brick Co, founded in 1900 as a consolidation of numerous brick manufacturing plants across New England and New York, had its offices. At its height, the company controlled over 30 brickyards in the Northeast, with NEBCO's "Harvard Bricks," advertised on this mirror,  extensively used in the 1910s-1920s construction of Georgian Revival buildings around Harvard University. An interesting piece of history, and spending any time in Boston and Cambridge, one will see bricks that look just like this one all over the place. The mirror is an uncommonly large and heavy for an advertising mirror--which seems apt! It was produced by Parisian Novelty Co, Chicago, established 1898, best known for its advertising mirrors of just this sort. I've done a good bit of searching and can find no other example of this out there but for one reference image of it on a website devoted to brick history! 

 3 1/2" d. Toning spots all over as evident but even so it reads very bright and crisp, with essentially no wear to the celluloid, clean edges and the mirror in very good shape, just a few tiny scattered spots, as there should be.