Remember that purple label did not spring forth fully-formed and all at once. immsmc, purple label started out as a designation with the Polo brand; in fact, I believe the first purple label goods carried the familiar Polo label done in purple rather than blue. At that point (which must have been 10 years or so ago) all Polo items were made in the US, so it's possible that your tie may date back to this time. I doubt you have a fake; any counterfitter worth her salt would reflexively reach out for the familiar Italian or English designations.
I'd be curious to see the back of the tie. As coincidence would have it, I just bought a couple of pl ties made of silk that could match your description of "somewhat thin and stiff." These are unlined seven folds in neat small scale woven silk patterns (one black w/ silver diamonds, the other brown and white checks). The effect is somewhat unusual and costumey, I suppose--evoking styles of the 1930s--but I find them quite beautiful.