I picked this one up on eBay just to see what it actually was:
It's marked "DEMI-.3 MINILINER JAPAN" and nothing else. Google has failed me completely, and while the two-material clip looks somewhat familiar, I can't place it. It has a simple Pentel-type mechanism in 0.3 mm. The lower barrel amd upper part of the clip are plastic, but everything else is metal.