The Helios 44 range is well known to be Russian made clones of the Zeiss Biotar. This is an early model Helios 44, with distinctive 13 blade iris. According to Camerapedia it is not quite the original first manufactured at KMZ Kraznogorsk Mechanical Plant (manufacturer of Zenith cameras) in 1957, that was Helios bayonet mount and 40.5mm filter thread rather than my M39, 49mm filter example.
No-x on mflenses has put together a list of helios variants. According to
his thread the 13 blade ones are all KMZ with serial numbers up to 02xxxxx. (serial numbers where the first two digits indicate the date came later and on other lenses, not the 44's). The earliest ones have a cyrillic letter on the nameplate and "5.8cm" rather than "58mm".
The 44 soon acquired the black finish, 8 blade iris and looks of the most common Helios the
44-2. Most 44's are M42 mount, as mentioned early ones are M39 screw fitting (but same registration distance as M42, a cheap M39 to M42 adapter is all that is required), and later some were made in PK mount - the 44-K-4's see listings.
Also according to Camerapedia, the Helios nomenclature is: Helios-44X-N, where X -is the index of lens mount (M for m42 thread, K for Pentax K bayonet, Д for Zenit-D bayonet) and N is a optical resolution index 2, 3, 4, 5, 6, 7 (the higher number the higher is an optical resolution of lens).
Focal Length: 58mm
Optical Formula: 6 elements in 4 groups.
Aperture Range: f/2 - f/16.
Minimum Focusing Distance: 0.5 m
Number of Aperture Blades: 13
Filter Diameter: 49mm
Weight: 230g
My example is a bit too worn and scratched to provide a review. I cadged some more pristine pics online. One shows an MMZ Minsk mechanical factory made example (see
logos here), however this is an 8 blade variant from rather later -1960's. Pic 5 shows my Helios 44 fitted with a 40mm taper washer (see link below) to prevent any light leaks around the mount - the narrow base does not cover the gap between a M42-PK adapter and the K mount.
I have posted a relubing guide
here.
Tips on using Helios 44 with pentax M42 adapter (loose fit, light leakage around mount edge)
see this thread.