original c. 1860's civil war-era american "mercury" or silver glass doorknob containing a cast brass tapered stepped footed shank. contrary to belief, these glass doorknobs never contained the toxic metal mercury. instead, the knobs was coated on the interior with silver nitrate, then affixed to the shank. these doorknobs enjoyed widespread popularity primarily in northeast cities, along with stately mansions of the midwest between the 1850's - 1870's. the footed shank contains a nickel-plated finish. likely fabricated by the nashua lock co., nashua, new hampshire. measures approximately 2 1/4 inches in diameter.