Being from a metrology background, I can understand the importance of this problem.
A few years back, the NIST (formerly the NBS) was working on an electrical representation for mass / force using a huge magnetic coil type device. I guess they still have not perfected this standard.
It basically would be a device that would exert a certain amount of force when a known current was passed through the coil...........
The high point of my career was making a silicon IR photodiode that forced the NBS to recalibrate its standards.
It was either that or admit my sensor had better than 100% quantum efficiency...
There was an article last year on the NIST effort with magnetic coils, and a competing team from Germany trying to come up with a new standard:
Wouldn’t the force change it the coil gathers contaminaton?