In 1963, South Carolina used white helmets with an "SC" logo on the sides and with a single dark-colored stripe; I have no color photographs of these helmets, so I cannot yet determine the color of the "SC" or of the stripe (which are very probably either black or garnet/red).
 I decided to draw this helmet using garnet for both letters and stripe. 

During 1964 and 1965, two different helmet designs were used: a garnet-colored one with a white "SC" (different from the 1963 version), and a white helmet with the same "SC" in some unknown dark color (I suspect garnet more likely than black). Neither of these designs featured any stripes on the helmet.
 I decided to draw the white helmet using garnet letters instead of black. 

On these helmets, the gamecock is clutching a banner on which is printed the phrase "Scholarship - Leadership", which is obviously not legible at this size.
 (Click HERE to open a pop-up window with a representation of the logo that I created.) 

Coach Paul Dietzel awarded black helmets to his senior players during at least parts of the 1973 and 1974 seasons, possibly only for the annual games against Clemson. I have also received some photographs from games during the 1970 and 1972 seasons in which at least some USC players are wearing black helmets like this one, but without the stripe.

The size of the logo may have varied somewhat during these years.

The 1982 helmet featured an "asymmetric" stripe sequence: the white middle stripe was bordered by a red or garnet stripe on the left, and by a black stripe on the right.

During at least the 1996 season, a "special teams player of the week" was "awarded" with the opportunity to wear a single, rather wide white stripe on his helmet for the next game.

A mid-season switch to this design was made for the fourth game of the 2000 season. A slight widening of the garnet stripes may have been made for the 2001 season.
 This style was reinstated in 2005 by new head coach Steve Spurrier.