Years	Decal	Shell	Mask	Stripes L to R	Stripe Width
?-1946-to mid 1950's-?	none	white	gray	crimson
?-1957-1965	small crimson player's #	white	gray or white	crimson	1"
1966	oval, white, interlocking "OU". O above left of U	lt. crimson?	gray or white	none
1967-1976	block, white interlocking "OU". O above left of U	lt. crimson	gray or white	none
1977-1999	block, white interlocking "OU". O above left of U	crimson	white only	none
2000-current	block, white interlocking "OU". O above left of U	metallic crimson	white	none
2003 special*	none	white	gray	crimson	1"

Notes:
Around 1977,  Sooner  helmet's changed to a darker shade of crimson. The 1971 photo below shows the lighter shade.

* - Worn in the opening game of the 2003 season vs. North Texas

Credits:
Thanks to Paul S. for providing the following OU historical information:

"I have some information that I hope helps in history of OU football helmets.  Most of my information comes from reviewing Sooner Century by J. Brent Clark., and When Football Becomes War by Robert Heard.  It appears that  helmets were used by some players at OU, by 1915.
 I don't know the first year OU had uniform colored helmets versus natural leather color, but I saw that OU had what appear to be crimson helmets with white multi criss-cross stripes in 1937-38.   In 1939-40, OU had a crimson helmet, with a block O on the front.  In 1941-45?, OU had crimson helmets with white cross pattern stripes (2).  The white helmets with crimson stripe were in use by 1946. In 1957-65, there were small crimson numbers on the helmets.  The first crimson helmets in the modern era were in 1966 under Jim Mackenzie.   It was also the first year with the interlocking OU.  In 1966, the O and U were used.  The style of OU was oval in nature.  The current block OU was first used in 1967.  The first year of white only facemasks was 1977, with few exceptions."

Thanks to Danny B. for the 1966 photo derived from the Sooner Century, 100 Glorious Years of Oklahoma Football by J. Brent Clark.

Oklahoma 1960	Oklahoma 1966	Oklahoma about 1971	Oklahoma 1998
Oklahoma 2000	Oklahoma 2003 special