A close variation of test card G on that page is common in a long list of countries, as it came from a highly successful commercially available test-card generator, and the pattern has since been copied and modified all over the place:

https://en.wikipedia.org/wiki/Philips_PM5544

That's a great link, thanks. I was actually looking for an image of testcard 61 (at the bottom of that page), a copy of which I saw being used only a few years ago!

57 is interesting too; the black square in the centre is actually a hole leading into a box lined with black felt, to provide a black reference.

The generation and use of test cards and patterns is a surprisingly complicated subject; even in the digital age.

Wikipedia also has some information on https://en.wikipedia.org/wiki/Carole_Hersee

A popular test card in the US, which you can still see in some digitizations of black-and-white era recordings, is RCA's "Indian Head" card, named after the line drawing at the top for subjective sharpness checking:

https://upload.wikimedia.org/wikipedia/commons/1/1b/RCA_Indi...

I'm rather fond of that test pattern because it was usually generated by a dedicated piece of hardware that scanned a CRT beam across a metal plate with the image on it. This was to produce a more reliable source image than the more common practice of pointing a camera at a test card in the studio - and is an odd predecessor to today's test-pattern generators.