It's 1.37M on B&M's in the states. 56 inches I think (or is it 54?) Anyway, it's just a rounding thing I think.
B&M will have a set "margin" for their limits. The local country H&S will say where abouts they deem it safe for the height limit to be. In the UK (and most of Europe) it's 1.4M. In the US, 1.37M.
I'll bet that in reality, B&M have it tested safe for even smaller sized people, it's just that you then have to add in a safety margin.