O Gauge 

O Gauge Coarse Scale 

Coarse Scale O gauge Was Common in the 1920-1950 but is much less so these days with most modellers electing to go for the finer scales 

The exception to this is, of course, the Collectors  of older trains and some of the new product by ACE  ETS and Others

The "Hornby Railway Collectors Association of Australia  is well know and a link to their web site is in the links page 

O Gauge Scale 

Fine Scale O gauge was very uncommon in the 1920-1950 but is much less so these days with most o gauge modellers electing to go for the finer scales 

Fine Scale O gauge is very expensive unless one id Prepared to scratch build . However on more recent times companies like Bachman have entered the field with mass manufacturing making it easier for modellers to afford a small layout