Additional information on “ELPRO” (thanks Mike):
The term “Elpro” means “Ernst Leitz Proxar”, and was introduced with the original Leicaflex. An Elpro is a close-up lens, not a filter, which fits the filter thread of the lens for which it is designed.
The Elpro was the first two-element achromatic close-up lens, computed for maximum quality with the Leica R lenses. Minolta, Panasonic, and Nikon copied the concept, and Nikon still makes a few to assist specific Micro-Nikkor lenses.
Leitz originally used the name “Macrotar”, but this name proved to be already trademarked by a now defunct New York City retail dealer. An original Leitz Macrotar is a very rare Leica accessory.
Via Digicame-info
