M39 to Micro Four Thirds
These are some of the least expensive adapters starting at $5 each. Spend a few dollars more for the adapter with an adjustable chrome bushing so you can align your lens’s focusing scale.
Jupiter 8 or 50mm f/2 Sonnar?
The Jupiter 8 is a Soviet copy of the Carl Zeiss Jena 50mm f/2 Sonnar used on the Contax rangefinder cameras. The 50mm Jupiter 8 in M39 has a focusing helicoid in the lens but it lacks one in the Kiev/Contax mount. Kiev and Contax bodies have focusing mechanisms for the 50mm lenses built into the cameras.
If you want to use a 50mm Sonnar on your MFT camera, you’ll need to spend $100-300 for an adapter that has a focusing helicoid. Lens adapters for telephoto lenses that use the outer bayonet on the Contax sell for around $15.