Back when I had a Nikon system for film (which I still have most of), I had a bellows, slide adapter, reversing adapter, and used the 55mm f/2.8 macro forward, and the 20mm f/2.8 wide angle backwards, to get some extreme macro shots (that needed a LOT of light). Slide duplication worked very well, depending on the film used. For B&W I was able to make slides from negs with fairly good results after finding the right film and developer (Tech Pan with a contrast compensation developer to make slides from negs made from Tri-X).
The bellows eventually crumbled and I didn't replace it at the time. It was discarded when I last moved. I still have the lenses (and the FM-2 and FE-2 I used them on). Conditions are unknown. I cannot find the reversing adapter or the slide adapter. I do have some extension tubes for Nikon mount.
I've decided to make the switch to Canon for digital, starting with a 450D. I'm looking at either the 7D or 5D to get by spring. I'm ordering the 60mm macro for now, and the 100mm macro L version next (even if I get the 7D, but a must for the 5D since the 60mm is probably locked out).
I have thousands of slides and negs from film days.