F.W. & R. King, 1852, Trade card for F.W. & R. King, (successors to James Green,) Manufacturers of Mathematical, Philosophical, Optical, Surveying, and Daguerreotype Instruments, No. 33 South Street, Baltimore.", Trade card, Ebay, LL/80006

F.W. & R. King, 1852, 2 April, Newspaper advert for F.W. & R. King, (successors to James Green,) Manufacturers of Mathematical, Philosophical, Optical, Surveying, and Daguerreotype Instruments, No. 33 South Street, Baltimore.", Newspaper advert, Internet - Original source ill-defined, LL/80007