MELCHIOR, ARMSTRONG, & DESSAU,
Here is another mystery company, but for reasons quite different than the cancel for a firm that is long dead and has left no trace by the year 2011. Melchior Armstrong & Dessau draws 100s if not 1000s of Google hits. Virtually all of the hits are for commercial websites that list or rate heating and cooling contractors in local areas, particularly on the east coast of the United States. These businesses all appear to be locally owned, small shops. However, there is not an M, A & D website that I can find. The firm clearly existed, and was doing big things in 1900 when this stamp was cancelled.
Dave Thompson sent this scan and had some doubts about the spelling. I think I've got that one solved but need a bit more help in pursuing exactly what kind of business this firm was doing in 1900.