The D-anchor-C is indeed found on the Brazilian Enfield. A Belgian book I'm translating identifies this rifle as the Brazilian Model 1855, made for the Brazilian Navy. The first 1,500 examples of about 6,000 imported reached this country in July 1861, bought by the State of New York and issued to New York marine units. The "D-C", however, is not the mark of O.P. Drissen. These guns were made by Malherbe or Ancion, and the author of this book thinks the D-anchor-C may be the "mark of a Northern Navy Yard", as this mark also appears on Colt revolving rifles and sabre bayonets from Solingen.