Caliper Vernier keyring Accurate Metric

Print at 0.1mm layer height for accuracy.

slide the two parts together and then insert the key ring to secure them together. 

The marker on the sliding part can be printed with a filament change to have it stand out, or it can just be covered with a permanent marker.

I printed mine with a brim to prevent warping, this requires it to be trimmed off to allow the other part to slide.