I'll be interested in the Nikon mount conversion for this.  I have a couple of these, one a screw mount, and one a Praktina.  I'm currently using them as macros.  The Praktina is in the remains of the mount for a zoom lens, and manages to focus out to a few feet away, making it not so bad for outdoor bugs and flowers.  The mount fouls the semi-auto button just enough so that you can use the aperture reset as a preset.  The screw mount, I found, fit onto a screw-thread extension tube that's so sloppy that the tube screws well into a T adapter, making a pretty nice close macro.  This one is fully manual.  
I tend to forget sometimes what I've taken with what, so here are a couple from tonight.  Hand held, so the focus isn't super-duper.  The cactus flower was with the Praktina mount and the Peugeot with the screw mount.  That's a Dinky toy 203 I got when I was about 3 in France.