00 gauge (or 00 scale, also spelled OO scale) model railways are the most popular standard-gauge model railway tracks in the UK. This track scale is one of several 4mm-scale standards used, but it is the only one to be served by the major manufacturers.
Despite this, the 00 track gauge of 16.5 mm is notoriously inaccurate for 4mm scale, and other gauges of the same scale have arisen to better serve the desires of some modellers for greater scale accuracy.
What's it worth? Take a look at this Oo Gauge price guide: sold listings for a value indication.