Unfortunately nobody recognises the universal currency sign, so from a usability standpoint it doesn't make much sense to use it.

And thus, by definition, it is NOT universal! (sorry, couldn't resist)

Agreed. Use 3-letter currency codes if you don't have a symbol.

Why is it 3d? That makes it really hard to figure out what shape it is.

From http://ascii-table.com/pronunciation-guide.php (They, too, stole it from somewhere):

In the socialist countries, they used and are using all kinds of IBM clones (hardware + software). It was a common practice just to rename everything (IBM 360 → ESER 1040, etc...).

Of course the "dollar" sign had to be renamed - it became the "international currency symbol" which looks like a circle with 4 rays spreading from it: ¤ Because it looks like a (small) shining sun, in the German Democratic Republic it was usually called "Sonne" (sun).

I’m one of those few people who knew what this symbol meant: the character was a standard symbol in the “MacRoman” repertoire before the introduction of the Euro replaced that code point (high-ASCII code 219, or shift-option-2) about the time of Mac OS 8 or 9.