GOMZ "Ortagoz" 1:4,5 f=13,5 cm Review
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GOMZ "Ortagoz" 1:4,5 f=13,5 cm (Russian name “ГОМЗ «Ортагоз» 1:4,5 f=13,5 см”) — one of the first Soviet lenses. Produced since the early 30s through the early 40s. For the "Fotokor №1" — the first Soviet serial camera with a film size 9x12 cm.
Lens has Dialyte/Celor optical design, there are opinions that it is a copy of the Goerz Celor lens. Lens assembled in the central shooter. Aperture has 10 blades.
The lens is composed of two parts. The front of the barrel is connected to the valve body. The rear unit unscrews out. 
I spent a little prevention — wash elements of a half-century dust and blackened ends. and blackened barrel inside, it had silver aluminum color. 
For mount the lens on Nikon D3100, I needed the focusing
helicoid and one long extension ring and the adapter M42-Nikon.
There are articles about the mounting Large Format Lenses on DSLR Camera and Using Large Format Lenses on DSLR camera.
GOMZ "Ortagoz" 1:4,5 f=13,5cm Sample Photos
Here is the test shots. Because the lens does not have coating, the picture is weak contrast. All pictures shooted at wide open. RAW export without post processing. 
Infinity test And some close focusing shooting
A few street shootings.
And some portraits
Summary GOMZ "Ortagoz" 1:4,5 f=13,5 cm has more historical value because of most of the reportage and amateur shots made in the Soviet Union in the 30-40-ies by this lens.
