In 1964, the Dallas Cowboys changed their helmet shell from white to the silver that they still wear today. The helmet logo, a five-pointed star, stayed essentially the same -- but they were considering going in a very different direction.

An old wire service photo taken on Feb. 5, 1965, shows team owner Clint Murchison, coach Tom Landry and general manager Tex Schramm examining two helmets, both of which appear to be silver. One has the familiar star logo, but the other shows a cowboy boot:

@21stCenturyTim @UniWatch That apparently is a rejected prototype from when they switched from white to silver. pic.twitter.com/VwwluBUj1P — Tom Farley (@tomfoolery815) August 21, 2016

Obviously, the Cowboys chose to stick with the star. The boot logo was never used, but it has been the subject of considerable "What if?" speculation by Cowboys scholars and NFL uniform researchers. The folks behind excellent helmet-centric website Helmet Hut have gone so far as to create a reproduction of it, giving us a better sense of what might have been (further info here):

Helmet Hut reproduction of Cowboys prototype shown in '65 wire pic (h/t @NFL_Journal). More: https://t.co/F9ErRDaWrd pic.twitter.com/t8KsMwiazI — Paul Lukas (@UniWatch) August 22, 2016

Prototypes like these are more common than you might think. Teams usually experiment with several different uniform options before settling on one design. Most of those options never make it onto the field, but some of them end up living on in the photographic record. Here's a look back at some NFL prototypes that, like the Cowboys' 1965 boot logo, ended up getting the boot. Some, like the Dallas example, are from several decades ago, and others are from more recent history.

1. Probably the most famous prototype in NFL history is the San Francisco 49ers' notorious redesigned helmet from 1991, which provoked such universal fan backlash that the team abandoned the whole idea and basically said "never mind" six days later -- but not before the new design was enshrined in the official NFL Style Guide. (The full story of this logo's creation and eventual retraction can be found here.)

49ers owner Eddie DeBartolo Jr. and coach George Seifert unveiling team's new helmet (which was never worn) in 1991. pic.twitter.com/P9B4qpCHqK — Paul Lukas (@UniWatch) February 22, 2016

Very rare: Official 1991 NFL Style Guide sheet for the 49ers, showing the new helmet logo that was never used. pic.twitter.com/oNtvedjJ0w — Paul Lukas (@UniWatch) February 23, 2016

2. The Cincinnati Bengals wore a plain helmet design for the first 13 years of their existence before switching to their current tiger-striped shell in 1981. But they almost went with stripes right from the get-go, as seen in this photo of team founder Paul Brown considering various prototype designs prior to the team's first season:

Did u know the Bengals' helmets almost had stripes on day one? Owner/coach Paul Brown poses with one such prototype. pic.twitter.com/5GfibJgpgW — Super 70s Sports (@Super70sSports) January 31, 2016

3. The Cleveland Browns have stubbornly and famously remained the only NFL team without a helmet logo. But in 1965 they were considering a "CB" logo. Despite rumors of the logo having been worn in preseason games, it was never worn on the field in any capacity. It lives on, however, in vintage NFL program covers, department store ads, and promotional merchandise (additional info here):

Browns' phantom "CB" logo. Never worn on field but used on programs, ads, promo items. More: https://t.co/9U4AKoOEEd pic.twitter.com/L7da8FIufE — Paul Lukas (@UniWatch) August 22, 2016

4. In 1993, the New England Patriots replaced their Pat Patriot mascot with the Minuteman character who has become known as Flying Elvis. But 14 years earlier, in 1979, they had been tinkering with another Minuteman mascot, and they were so serious about it that they even announced that Pat Patriot was being retired. But owner Billy Cunningham got cold feet and decided to let fans choose between the old and new logos during a halftime vote. Pat Patriot won in a landslide and the initial Minuteman logo was mothballed. (For more details on this story, look here.)

Patriots planned to use this logo in '79. Fans voted to keep Pat Patriot instead. More: https://t.co/0TBWZT3Jsb pic.twitter.com/LaqTUMfujf — Paul Lukas (@UniWatch) August 22, 2016

5. When the Tampa Bay Buccaneers switched from their original "Bucco Bruce" helmet design to their pewter helmet with the pirate flag logo, they considered a variety of other concepts. The team has displayed those rejected helmets at One Buc Place (further info here):

Bucs prototype options from 1997, when team switched from Bucco Bruce to pewter shell. More: https://t.co/1oIsNzUxFk pic.twitter.com/pKiBF4FcSO — Paul Lukas (@UniWatch) August 22, 2016

6. When the Houston Texans' franchise name and logo were unveiled in 2000, team and league officials posed with a white helmet. That was changed to the current blue shell by the time the team began play in 2002, but not before the white design had already been configured into the Madden video game.

Texans originally planned to go with a white helmet, as seen in this photo from team name/logo unveiling in 2000. pic.twitter.com/AH9ieX5xDH — Paul Lukas (@UniWatch) August 22, 2016

@UniWatch yes,madden 2002 had these helmets, game was for 01 season, as an expansion team in franchise mode for "02l pic.twitter.com/EOl8HBOzTn — L. Michael (@sweatpantz7) August 22, 2016

7. When the Seattle Seahawks updated their logo to look more ferocious in 2002, fans were offered a choice: The team could put the new logo on its longstanding silver helmet shell, or it could switch to a new dark-blue shell. Of the 64,513 fans who voted, more than 76 percent chose blue, relegating the silver option to the realm of unused prototypes.

When Seahawks adopted "meaner" logo in 2002, fans were given choice of silver or blue helmet. Blue got 76% of vote. pic.twitter.com/U3EYs4V8L8 — Paul Lukas (@UniWatch) August 22, 2016

8. When the Jacksonville Jaguars were named as the NFL's 30th franchise in 1993, the team was originally slated to wear an innovative uniform design featuring a leaping jaguar on the helmet and jersey shoulders. But the Ford Motor Company, which owned the Jaguar car brand at the time, felt that the leaping cat was a potential trademark violation. Although no lawsuit was ever filed, the team ultimately changed its uniforms before hitting the field for the 1995 season.

Rare pics of Jags' original "leaping jaguar" uni, which was scrapped due to legal pressure from Jaguar car company. pic.twitter.com/onQT6ixP6L — Paul Lukas (@UniWatch) August 22, 2016

9. The Jags weren't the only 1995 expansion team with a prototype that was eventually discarded. The Carolina Panthers had initially planned for their home jerseys to be blue, not black. "When the Panthers took the field in '95 wearing black jerseys [instead of the blue ones that had previously been shown], I called the team office to find out what happened to the blue unis," said Uni Watch reader Kevin Mericle. "Their PR guy told me that when they did some photo shoots of the blue jerseys in sunlight, it caused the dye to turn a brownish color." (Of course, that didn't prevent the Panthers from later adding a blue alternate jersey.)

Rare photo showing prototype of original Panthers home jersey, which was slated to be blue, not black. pic.twitter.com/u6SSIez5bA — Paul Lukas (@UniWatch) August 22, 2016

10. In 2003, Reebok prepared a series of new uniform designs for the Minnesota Vikings, with an eye toward bringing them onto the field in 2005. As it turned out, the Vikes rejected all of these concepts, but they offer an intriguing look into the road not taken. (For additional images and information, look here.)

Some of the many designs Reebok prepared for the Vikings in 2003. All were rejected. More: https://t.co/16XxX6xkMd pic.twitter.com/6Ls2NXoYDW — Paul Lukas (@UniWatch) August 22, 2016

There are still more prototypes floating around out there (and, almost certainly, dozens more that we'll never find out about), but you get the idea.

The general feeling about prototypes has always been to treat them as historical footnotes or oddball curiosities. But given how freewheeling the uniform scene has gotten in recent years, why not bring some of these designs onto the field for a day, as a "What Might Have Been" promotion? Some of them, like the Cowboys, 49ers, Browns and Bengals examples could be brought into the real world without even violating the NFL's current rules regarding helmet shells. And hey, just about all of them would be better than the recent Color Rush designs.

Would you like to nominate a uniform or uni element to be showcased in a future Friday Flashback installment? Send your suggestions here.

Paul Lukas thinks a "What Might Have Been" promotion featuring old prototype designs would be a big, big hit. If you liked this column, you'll probably like his Uni Watch Blog, plus you can follow him on Twitter and Facebook. To learn about his Uni Watch membership program, be added to his mailing list so you'll always know when a new column has been posted or just ask him a question, contact him here.