Gauge 2 Standards.
According to Elenora Steele (Greenly's daughter) and her husband
Ernest in "The Miniature World of Henry Greenly", published in 1973,
it was Greenly who prepared the first standard specification for
model railways and locomotives in 1899. His recommendations were
submitted to the Society of Model Engineers and were largely adopted
as the Gauges that we know today. A comment on the 'back-to-back'
dimension for Gauge 2 appears in the 1909 volume of 'Models,
Railways & Locomotives':

By Aug 1909 he appears to have adopted 1 25/32" or 45mm as the
standard 'back-to-back':


In September 1909 he published the data in a useful tabular form,
adding clearances for pointwork:


In October, he considered the track spacing or 'six foot way' and
came up with far more realistic dimensions than are often used
today. No doubt the savage foreshortening of tinplate coaches helped
in this regard.
