Steam pressure gauge of a steam locomotive, at the Darjeeling train yard (India)
The red mark indicates the maximum pressure that the boiler can support. The numbers on the gauge indicates 10x PSI (pounds per square inch), and those boilers are tested up to 140 PSI.
The Darjeeling Himalayan Railway, locally known as the "Toy Train", is a 2 ft (610 mm) narrow gauge railway that runs between New Jalpaiguri and Darjeeling (India). It is still operated by vintage British-built B Class steam locomotives. Operations between Siliguri and Kurseong have been temporarily suspended since 2010 following a Landslide at Tindharia (view photos of the landslide).
For more info about the DHR steam locomotives, read en.wikipedia.org/wiki/DHR_778_(locomotive) and www.irfca.org/docs/locolists/dhr-locos-full.html.
For more information about the Darjeeling Steam-powered Train, read en.wikipedia.org/wiki/Darjeeling_Himalayan_Railway.