Metabones C to Micro 4/3 adapter. Purchased on eBay.
Pros: Simple to use. One-piece construction in chrome-plated brass. Good mechanical fit to Micro 4/3 camera bodies. Machined groove to avoid contact with electrical contacts on camera body.
Cons: Expensive. Chrome plating is thin and starts to wear out after mounting and dismounting on camera just a few times. Plating is missing where the piece was suspended with a wire during electroplating (in high-quality electroplating, this is easily avoided by plating twice while suspending the piece at different points - this one was plated only once to cut costs). Does not allow the use of C lenses with wide bases, but this is a limitation of all C adapters (this adapter is thicker than others and therefore slightly more limiting in this respect). Shiny rear surface may cause internal reflections and lower contrast.