2 gauge

Gauge 2 (also called 2 gauge or II gauge) is a model railway gauge, originally, then standardised in 1909 at , a 20% reduction and a change in definition: from mm to inch. It has since fallen into disuse. The gauge was introduced by Märklin at the Leipzig toy fair in 1891. Gauge 2 was equivalent to a 1:22.5 scale.

Related scales and gauges
After the change to in 1909,  gauge was standardised as 3 gauge (or III gauge).

European G gauge trains are built to the same II gauge scale, but with a narrow rail gauge of (the same as 1 gauge). This G gauge at 1:22.5 scale represents narrow-gauge railways. This scale-gauge combination is sometimes called IIm in European literature.

In the UK, Gauge 2 was 2 inches (50.8 mm) while Gauge 3 was. From this, it follows that G gauge is sometimes, albeit rarely, referred to as 3m. A 2 inch (50.8 mm) gauge of standard gauge locos gives a scale of 1:28.25, not so far off the 1/29 used by some manufactures with gauge track. In the grand tradition of model rail gauges often being narrower than the full scale equivalent (00 scale being the classic example) this is deemed perfectly acceptable.