A very amusing lens which was designed to copy 8 or 16mm film to 135 format (aka full frame), to achieve this it's a very short focal length with a large amount of extension available. Due to the short focal length (I would guess around 15mm) it's pretty easy to get a tilted plane of focus, combined with a fixed aperture (I would guess f/5.6) meaning you have a thin slice of nothing in focus... It's also uncoated and flares if there's any hint of contrast (just to make focusing fun!). These were taken at about 3:1, anything higher than that has too little in focus (unless it's flat, it probably works better for film). The bevel/edge is around 1mm tall for a sense of scale. CYG11 scalpel, new and probably still sterile. CYG11 scalpel, used and showing some wear after cutting a lot of fabric (I don't think fabric wears them at all), ABS plastic (lots of shaving/cutting edges/flashing/sprue), aluminum (much the same as the ABS), and likely being used as a prying tool (what can I say? it's my precision prybar). It's still got plenty of life left in it, I opened a new one purely to take the first picture.