Standards.

[neilbourjaily]

At the risk of sounding dismissive or even careless, so long as the rule is not being used with another rule, then things should come out ok. Always use the same rule throughout a project. Truth be told, it's not likely a case of Stanleys would all read the same, though I'm sure a case of Sterrets would. It really makes no actual difference what the scale is, so long as it is used consistently. One can be their own bureau of standards.