In 1932, Zeiss Ikon (their now-defunct camera-making devision) introduced the Contax, a rangefinder with an odd dual-bayonet mount. Wide-angle and telephoto lenses mounted to the external bayonet and functioned just like lenses on any other camera. Normal lenses, however, did not feature a focusing mechanism in the lens. Instead, they attached to the camera's internal bayonet, which had a helicoid built in to the camera.
In 1947, the Soviets began producing a copy of this camera at their Arsenal plant in Kiev, creatively calling it the "Kiev". They also produced two other rangefinder lines, Zorki and Fed, using the more conventional M39 Leica Thread Mount, or "LTM". But the Kiev cameras, with their odd mount, continued for decades, long after Zeiss gave up on making their own cameras.
Anyone who's searched eBay for Soviet lenses has probably noticed odd-looking, cheaper versions of lenses "for Kiev/Contax". The fact that the focusing is done in the camera makes adapting them to modern cameras difficult, and the dual-bayonet thing is just confusing. Nearly all Soviet rangefinder lenses had both LTM and Kiev-mount versions, so it's easy to just stick to the threaded ones, which will always work fine with a dirt-cheap, simple adapter.
The only exception is the Helios-103 53mm f/1.8, introduced in the late-70's as the new standard lens for the Kiev-4M. There is no LTM version of this lens, and it requires the use of the inner-bayonet focusing mechanism built in to the Kiev camera. Fortunately, some eBay sellers in Ukraine are gutting old, broken-down Kiev cameras and combining the relevant parts to generic adapters for the rangefinder's modern replacement: mirrorless cameras. They sell these crude-but-functional adapters for about $40 shipped, and for $10 or $20 more they will include a lens, such as the Helios 103, as a "free gift".
One of these arrived in my mailbox from Kharkiv on Saturday. I'm not sure anyone ever used this copy of the lens since it was made in 1984. It looks brand-new.
Despite its tiny size, it uses the same "planar" 6-lens-in-4-groups formula as all Helios lenses. Its rendering is very similar to the Helios-44.
A little test indoors the night before showed that the lens is razor-sharp in the center even at f/1.8. Further testing the following morning showed that the lens is sharp nowhere else at this aperture, even when accounting for the strong field curvature, with some of the "glow" you might expect from a lens formula which had changed little since 1896.
The background rendering actually softens at f/2.8, with the highlights losing their bright, hard edges.
It's a cool little lens I just had to try, but for others I'd say it's not really worth the hassle of the weird mount when the Helios-44 already exists, unless you're in the market for a rangefinder Jupiter-9. The price difference between a Kiev and M39 Jupiter 9 is less than the cost of one of these adapters, even with the lens.