470R:
Perhaps one might expect a rack-number in Sanskrit on earlier guns, but between the wars in India it was all about "being British"! The guns were British, the visiting dignitaries were invariably British, many of the Maharajahs were educated in Britain and indeed some of them spent the summers in England as guests of Brit royalty. An armoury-number in western numerals is no surprise IMHO.

Here's a close-up: