This is the Admon 918 105mm f/2.8 industrial lens, other than name, focal length and aperture that’s the extent of what we know about this lens. This lens came from a seller in South Korea for the absurd price of $25 (lens only). There is no information on this lens available online and the focal length and f-stop are measured. The construction and fast aperture make the lens look like a high performance optic but I really have no idea to be honest, the lens might not even be corrected for visible light for all we know.
These 3 photos from the eBay seller’s ad, sorry for the poor quality, are interesting. Judging by the extension, about 150mm, it looks like the 918 lens is being used about 1.5x and reverse mounted, with the camera on the far left set for higher magnification. Also the line scan camera sensor is shown in one of the images and it looks like the line scan sensor is right about 43mm wide. So the 918 lens should cover a full frame area sensor.
Name: Admon
FL: 105mm (measured)
Fixed aperture: f/2.8 (measured)
Aperture in reverse: f/3.3 (measured)
87mm x 49mm
No accessory or mounting threads
Wavelength range: unknown
Source: unknown country (this copy came from a South Korean source)
I’ll create a page for this lens once I am able to make time to test it. If you have any information on these lenses please send me a message. Thanks.