The problem with the Imperial System is all the little inconsistencies,like the fact that US Gallons are smaller than British/Australian ones,so that a "44 Gallon drum" in Oz translates to a "55 Gallon drum" in the USA.
They are both,thankfully,near as dammit to 200litres.
Old Brit type equipment is likely to have Whitworth,UNC,UNF,BA (AAARRRGH!),or BSF (double AAARRRGH!) screws,while the smaller screw sizes used in US equipment are of a incomprehensible & completely incompatible series.
In the larger sizes,UNF is pretty much common to both,some UNC,SAE,& Whitworth are compatible in very large sizes.
Even metric screws have weird things,though.--- small Japanese metric screws were different to the same nominal size German screws---though this may have been sorted out in more recent times.