nightjar cpb@ wrote:

I had a similar experience when I took over the manufacture of a
medical device.
[...]
However, if you actually made it to those drawings, the product did
not work. I knew the product had first been made in the 1950s, so
would have been designed in Imperial measure. Once I had converted
things like 'hole 16mm dia fit H8' to 'drill through with 5/8"
drill', it worked.

I'm trying to think what kind of device would involve that kind of
precision and have been made unchanged since the 50s. Care to enlighten me?

Pete