​In Engineering school at U of T, we were taught in a lab course that it
was best practice to use instruments rated for one decimal place greater
than what you needed to be certain of.  So if you needed a "good" thou
measure, then you should spec a tool that capable of measuring down to
tenths, one decimal over.  I have no idea if that is still true today, with
all the fancy optical and electronic digital wizzbang gizmocity available
now. I was just thinking that the DEC computer I used to program in the
1970's (punch cards and Fortran!)  took up the whole basement of the
building and required special cooling systems, meanwhile today, that little
cell phone in your pocket right now is literally thousands of times more
powerful.

And also, duh, I just realized the Tumico probably stands for Tubular
Micrometer Co.  Weird, it didn't occur to me before you mentioned
'tubular', haha- ( Somehow, I pictured a shortish Japanese man with a small
moustache- a nice Mr. Tumico- who made it to the big time by building very
nice micrometers in the USA).
Cheers from Waterloo
Claudio
PS it's after 5, I'm off duty, and I am gonna dip into a private stash of
some single malt. (Wish I good push a little bit of it down the intertoobs
to share with you all.  Who knows, maybe with future versions of 3-D
printing, it will be possible some day, meanwhile, I will just pass the
electronic spittoon along instead )