I picked up one of my guitars from having a little spa type work, setup, frets polished.. noisy pots cleaned.. Got to talking with the owner about old tools and such... and since we hit it off he gave me a ruler that he got from an old timer who work at DuPont..
Interestingly it has a dimension correction for temp, however, it doesn't indicate the temp..
9/32in/ft on a 2 foot rule
