The Helios 44-2 is one of those lenses that every photographer should have at least tried. It's a "classic" and photos taken with it breath an air of bygone days. And it's cheap... Even your M42-NEX adapter may cost more :) The Helios 44-2 is said to be the Russian version of the Carl Zeiss Biotar.

Many versions of the Helios 44-2 exist: Latin or Cyrillic script, different factories, ... My copy is made in Valdai and uses Latin script. Princelle lists it as K1760.

Aperture range: f/2-f/16
Minimum focussing distance: 0.5m
Aperture blades: 8

You can look at its dedicated gallery on my website or at my complete Gallerie de gear:

The ARG-file I use with exiftool for this lens: helios44-2ValM42.txt

-n
-XMP:Lens=Helios 44-2 58mm f/2 (Valdai) (M42)
-XMP:SerialNumber=84215156
-EXIF:MaxApertureValue=2
-EXIF:FocalLength=58
-EXIF:FocalLengthIn35mmFormat=58
-EXIF:FNumber=2