DIY adapter with focus trap for industrial Nikkor

I have this Ultra-Micro-NIKKOR 55mm f2 lens. It mainly was used in early semiconductor lithography in the 1970's and possibly into the 1980's. I have its sibling, the Ultra-Micro-Nikkor 28mm f1.8, as well, but I have not yet found a photographic use for that lens (due to its tiny image circle). It is a fixed focus lens. You need to move the camera to move the focus plane.

A number of years ago I have made an adapter for it for Canon EOS, consisting of a camera cap (for the EOS bayonet side) and a M42 lens mounting plate from a Durst enlarger (for the lens side). Both are of a similar plastic, so I glued them together with an appropriate glue.

To make trap focus work, I got the contacts block and the electronics board from an old Sigma 70-300mm DL lens. The electronics make the camera think there is an AF lens mounted. Since the camera notices the lens does not smoothly communicate during the "AF process", it waits with taking a photo till the AF sensor sees a subject actually in focus.

This is the lens:

Here it is on the right, it its wooden box. On the left its 28mm sibling.

This is the adapter, with exposed electronics:

Camera side, lens concat block clearly visible.

Lens side.

Test images to see if/how focus trap worked, with center AF point, 100% crop of center:

Here some examples taken with it, on a Canon EOS 450D:

2 images stitched, focus trapped in lady bug. OF points other than the cross type center point work fine too.

Regrettably, the lens has a bit too small an image circle for FF at the distance  to use it on my 6D without cropping or TC. On EOS M you can't use it for focus trap because the mirrorless camera lacks the PD AF system's focus confirmation that triggers focus trap.