I know it was the early 90s when Prince did the name change thing but I also know he was using the symbol as a sort of logo before that. Does anyone know how far back it goes? When was the first time he used it? Thanks

The earliest I recall seeing it is on the 1999 cover.

Take a good look at the cover of the Purple Rain album.
[Edited 4/28/16 6:50am]

CuddlyBear said:

Didn't think about that, but yes, it's there too.

And part of the enhanced (flourish) symbol is actually an alchemist symbol for soapstone. There's a story about how some dude named Mitch Monson struggled for two days with another guy to come up with an enhanced symbol for Prince. They labored, etc., and came up with it. But the truth is that it's been around much longer.

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The simpler version was on the 1999 album (1982), at the bottom of the first 9.

It was also on Prince's motorcycle in Purple Rain, and on various pieces of artwork for the singles (namely the back of the "Let's Go Crazy" single).

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The flourished version showed up by 1992's album:

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I think the simpler version was still in use during 1991's Diamonds and Pearls, but by 1992, the above enhanced version appeared.