Henry Craig patented his fused glass lens in 1862. The specimen on the glass slide was pressed against the bottom of the lens, when in focus, so no focusing mechanism was required. Both gutta percha and sheet brass versions of the Craig microscope were made, and not all gutta percha versions are identically shaped.

The Craig microscope was advertised in many agricultural and other magazines in late 1862 and 1863. The Dec 1862 ad in the American Agriculturist was illustrated with a longitudinal cross section of the microscope, similar to the patent illustration. Subsequent ads used a cut of the actual microscope, with the earliest resembling the brass models. Henry Craig's 1862 ad states that his microscope had just won a silver medal at the Ohio State Agricultural Fair. A number of magazines printed Craig's press releases, sometimes, apparently, word for word. Several even reproduced the grossly misleading cut shown at the left, in which the small toy appears the size of a large drum microscope. The Craig was, in fact, a rather high power toy microscope that may have served its many owners every bit as well as as the imported toy drums of the time. The unique fused lens and attractive gutta percha body have earned it a place in any American microscope collection.