Thank you Jacksterp!

Yes, a labour of love. It is designed for use, not for looks, and certainly not for ease of fabrication. Not commercially viable : too much work, too much breakage. When excellence is the goal, time invested doesn't matter.
Once the design is proven, maybe a more industrial production method could be explored, but that is quite a way's going yet.

Here is my poor man's DRO :



Digital callipers fixed with some neodymium magnets, and a 50 mm dial indictor on the cross slide, clocking on the tool holder. It's quite good, repeatable within 0,01 mm

Fitting new parts :



from left to right : the body, with the section hidden in the nubbin at the end, the piston floating inside, the blind cap screwed on the body and the piston retaining ring. Nicely concentric, with rather tight tolerances.

More to come!