@Arthur P. Bloom posted:And let us not forget an inconvenient truth that original sizes (gauges) of toy trains were NUMBERED. There was, at least, #1 Gauge, #2 Gauge, etc. When trains got smaller, the next obvious and logical step was to name them "zero" gauge, which looks like this: 0. Not like this: O.
And “double-aught” 00 or OO in Britain. Although don’t say that O was originally “zero” too loudly in the other forums as a few folks might yell at you and say “IT’S OH, NOT ZERO!”
Even HO was originally H with a zero (H0) or “ha nul” in Germany… where it was invented.