As far as I know, the "sputnik" currency symbol is still used as a placeholder in some text editors and spreadsheet programs and such. This was always a substitute symbol to be used when a proper symbol wasn't available for any given currency, though, and had nothing in particular to do with the euro. However, since it saw such little use, many font foundries placed the euro symbol in its slot for a while as a hack to make the euro available before proper Unicode encoding became prevalent.

There used to be the "ECU" which had the ligated CE symbol, but that was barely more than a conceptual finance basket when it was replaced by the euro hard currency.

Another name for this useless character is louse.
And it "has no typographic function. It merely holds a place on the font ..."
See Bringhurst, The Elements ..., p. 305

Useless!? It's essential for setting the word "C¤sm¤naut"

Absolutely, Sii :D

The running joke back when I went to high school was that this was a symbol for Roubles. On the keyboards of Yamaha computers we had in a computer lab the symbol sat between $, £ and ¥, so it implied it was a currency sign. And since the lab together with the high school was in Russia, it was only natural to assign the symbol to the Roubles :-)