This British Standard specifies requirements for the construction,
accuracy at the reference temperature of 20 °C and the protection
of metric and imperial precision vernier depth gauges. It applies to
metric depth gauges that measure from zero up to 600 mm using a
main scale and vernier scale graduated to read to 0.02 mm. It also
applies to imperial depth gauges that measure from zero up to 24 in
using a main scale and vernier scale graduated to read to 0.001 in.