Rikenon 55mm 1:1.4. Not especially rare or anything, but it is all-metal construction and has a nice heft to it. M42 screw mount. I found an adapter that I can put it on my 5D2. I have also recently acrquired two Ricoh film cameras that it fits (natch!).
Canon 5D2, EF 50mm Compact Macro. 1/100s, f/8, ISO 1600. Off-camera flash.