Had never heard of Gauge 3 before seeing this:
https://www.ebay.es/itm/135523422533
And a little digging revealed:
https://www.gauge3.org.uk/
And:
https://en.wikipedia.org/wiki/Gauge_3_Railways
Among many other links, of course.
1:22,5 or 1:24 scale trains on 64mm gauge track. They must look bonkers up close and personal.
Some talk about O Gauge / 1:43 being too big, and Gauge 1 / 1:32 being beyond consideration, but Gauge 3 has to be about as big as one can go before ride-on scale!
I have one or two 1:24 trucks in the office, and they are insane compared to the 1:43 trucks at home.