A well known M42 mount lens from the former Soviet Union which performs very well optically. It has a reputation for excellent build quality, and is available in many variants. Models with an A/M switch make this lens easy to use on almost any camera. Many people have started to use manual focus lenses again because they've found a cheap Helios in a local shop or on the Internet, and its quality has amazed them.
I've got the 44-2 and 44-m, I rarely leave home without one.
These models are (or can be) multi-coated:
Helios 44-3 (always multi-coated, pre-set, 8 blades)
Helios 44M (both MC and single coated version exist, MCed is rare, A/M switch, 8 blades)
Helios 44M-4 (both MC and single coated version exists, auto, 6 blades)
Helios 44K-4 (K-mount, i believe this model is always MCed, auto, 6 blades)
Helios 44M-5 (both MC and single coated version exists, single-coated is rare, auto, 6 blades)
Helios 44M-6 (always MC, auto, 6 blades)
Helios 44M-7 (always MC, auto, 6 blades)
The MC (Multi Coated) versions of this lens include the 44-M4, 44-M5, 44-M6 and 44-M7. These are all 6 bladed lenses (earlier, non MC lenses had 8 blades), and are capable of providing excellent results and many hours of inexpensive fun in any hands.An excellent all-round performer with unique bokeh and colour rendering - this is a usable and affordable lens that should be part of every collection.