That's Not An American Ship... (Updated And Corrected)

...even though it sort-of looks like one.

In my slow trawl through my collection updating my database, I came upon this coin:

Saint Helena 25 pence 1973, issued to commemorate 300 years of British occupation.

I looked at it, thought "Hmm. Nice ship. And flags, too. Two of my minor collecting themes in one coin."... and then took a second look. What is that flag she's flying at the stern? St Helena is a British colony, and has been for a while (celebrating this fact was, after all, the whole point of making this coin). But that flag looks distinctly stripey. Here's a closer look:

So what's going on, here? It looks for all the world like an American flag with the English white ensign where the stars ought to be - or maybe the Greek flag:

But neither of those flags were in use in 1673 when this ship presumably sailed.

The coin was designed by Leslie Durbin, one of Britain's most prominent coin designers and silversmiths of the 20th century and maker of ceremonial regalia for church and state, so I think we can rule out incompetence, laziness or closet Republicanism. If the flag is striped, then it meant to be striped, and it means something other than the US of A.

The answer, which eventually occurred to me? It's Petra-Sancta blue.

If you don't know what that means, let me explain. Back in the middle ages, a fellow named Petra-Sancta devised a system to allow objects which were normally brightly coloured (such as flags and coats of arms) to be illustrated on things which normally weren't coloured (like printing, coins and sculpture). Here's the system he devised, as depicted by Encyclopaedia Britannica; you can find a similar illustration at the front of the old Craig catalogue of world coins (a feature sadly lacking from today's Krauses).

So, if you wanted to "colour" part of a coin yellow, you'd fill it with dots - and everyone who needed to know would know that it was supposed to be "yellow". Horizontal stripes mean "blue". In this modern age, hardly any coin designers use or even know about the Petra-Sancta system; it seems to have mostly gone out of fashion after World War I. But Leslie Durbin obviously still used it.

So our mystery flag is merely the English blue naval ensign. Pre-1701, it looked like this:

which exactly matches what we see on the ship on this coin. So, thumbs up to Mr Durbin for his attention to detail, even in the unlikeliest of places.

(flag illustrations are snitched from Wikipedia)