Courtesy of Justin Scott, Australia.
Additional R data courtesy of Douglas Herr of WildlightPhoto.com

anastigmat an anastigmatic lens system (Leitz Anastigmat (Leitz I) from 1920 with a fixed 50mm f3.5 lens. Produced again as a retro camera in 2000-2002).

anastigmatic (of a lens system) constructed so that the astigmatism of each element is canceled out.
ORIGIN late 19th cent.: from an- 1 [not] + astigmatic (see astigmatism):

astigmatism a defect in the eye or in a lens caused by a deviation from spherical curvature, which results in distorted images, as light rays are prevented from meeting at a common focus.
DERIVATIVES
astigmatic
ORIGIN mid 19th cent.: from a-- [without] + Greek stigma 'point' + -ism.

ASPH
Stands for "aspheric design". Most lenses have a spherical design - that is, the radius of curvature is constant. These are easy to manufacture by grinding while "spinning" the glass. This design however restricts the number of optical corrections that can be made to the design to render the most realistic image possible. ASPH lenses, however, involve usually 1 element that does *not* have a constant radius of curvature. These elements can be made by 1) expensive manual grinding, 2) molded plastic, 3) Leica's patented "press" process, where the element is pressed into an aspherical ("non-spherical") shape. This design allows the manufacturer to introduce corrections into compact lens designs that weren't possible before. Practically, the lens performs "better" (up to interpretation) due to increased correction of the image, in a package not significantly bigger than the spherical version.

Betriebsk
A designation engraved (or silk printed) on top of Leica cameras produced for internal factory use only. 25-50 Leica MP Betriebsk cameras was produced in 1957. But for the M7 for example, ca. 100 M7 Betriebsk cameras was produced, intended for Leica dealers to have as demonstration cameras.
ORIGIN None so far.

Compur
Curently no origin known. Leica I Compur camera (1926-1941) and Leica Summicron (II) Compur 50mm f2.0 lens (1959).

Elmax
Elmax = E. Leitz + Max Berak. Ernst Leitz was the founder of Ernst Leitz Optical Industry which later became Leica. Professor Dr. Max Berak was employed at Leica in 1912 and was the architech of the first Leica lens which Ernst Leitz asked him to design for the "Barnack's camera" (the 1913-prototype named after Oscar Barnack who invented it). The lens was a f/3.5 50mm and was known as the Leitz Anstigmat and later the Elmax.

f
the ratio of the focal length of a camera lens to the diameter of the aperture being used for a particular shot.
ORIGIN early 20th cent.: from f (denoting the focal length) and number

Four Thirds
The Four Thirds System is a standard created by Olympus and Kodak for digital SLR camera design and development.
The system provides a standard which, with digital cameras and lenses available from multiple manufacturers, allows for the interchange of lenses and bodies from different manufacturers. Companies developing 4:3 cameras and/or lenses are Fuji, Kodak, Leica, Olympus, Panasonic, Sanyo, Sigma. See www.4-3system.com

Leica
Leica = LEItz CAmera.

M
(as in "M3", "M6", "M7" etc.)
… stands for "Messucher", which is German for "Viewfinder". The "3" in M3 was chosen because of the three bright line finders for the 50, 90 and 135 mm lenses. Later the numbers of the M cameras were more or less chosen to follow each other.
"Meßsucher". It is always correctly written with the "ß". There are technically not three "s", rather the "ß" and one "s" because it is a word constructed by the combining of two precise words.
M-body evolution in chronologic order:
M3 - MP - M2 - M1 - MD - MDA - M4 - M5 - CL - MD-2 - M4-2 - M4-P - M6 - M6 TTL - M7 - MP - M8.

MOT
Cameras that has been prepared to be fitted with a motor winder to forward the film. For example the Leicaflex SL for manual winding and the Leicaflex SL MOT that is likewise born with manual winding, but can be fitte with a motor winder.

MP
Stands (also) for Mechanical Perfection.

Rangefinder (RF) Camera
A camera where the photographer is using a viewfinder to view and focus (measuring the distance) with; a camera where one is not looking through an actual lens when framing and focusing.

SLR abbreviation for Single-Lens Reflex; the lens that forms the image on the film also provides the image in the viewfinder via a mirror.

viewfinder a device on a camera showing the field of view of the lens, used in framing and focusing the picture; often also works as an instrument to measure the distance (focusing).