OPALAR GO-90 Hydro (underwater) Lens

This lens is an improved version of the "Hydro Russar" lens, for underwater use. field of view underwater is 82 degrees.
"Opal" was an experimental subdivision of LOMO.

Serial No. 0393 ( #3 made in 1993)
M-39 screw-mount (will fit M-42 with adaptor)
20mm / f.3.5 - f.22

Weight: 450 grams
Length: 2.25"
Diameter at front ring: 2.25"

This lens is an improved version of the "Hydro Russar" lens, for underwater use. There is no focusing ring as depth of field is so great. The front of the lens is covered with a blue-coated protective disk of glass, mounted as to be water-tight. Front and back elements are coated with a purple coating.

Made for use with a 35mm camera (possibly Zenit 3M or newer Zenits with M-42 mount adaptor ?).

Below is a photo of the original passport for OPALAR GO-90 serial No. 0393 with specifications, and it shows No. 0593 ... so at least 5 of these were made. Probably only a few of these lenses were made as prototypes. No. 0393 comes with a machined custom-made and fitted aluminum and plastic case with pencil writing on the bottom "03".

Patent information for "GO-1":
Hydro-lens “Opalar-GO-1” - 07.03.1993 / authors: Alexandr Vladamirovich Butsevitsky, Nikolai Borisovich Voznesenskiy, Andrey Viktorovich Ivanov, Ludmila Nilovna Kurchinskaya, Leonid Igor Przhevalskiy, Vladimir Vladamirovich Usoskin.