Gauge 2 is a model railway gauge, originally 64 mm (2+1⁄2 in), then standardised in 1909 at 2 in (50.8 mm), a 20% reduction and a change in definition: from mm to inch. It has since appears to have 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.
We would be delighted to hear from anyone who can show that rumours of it’s demise are greatly exagerated.