I looked it up and from what I can tell if you count the Eagles Bald Head helmet that originated in 1948 it would be the second NFL team to have a helmet logo if you can count that as a logo. The next would be the Eagles wings in 1954 and Colts whose Horse Shoes originated in 1954.

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Philadelphia Eagles Helmet
"As mentioned earlier, the Eagles were the second NFL team to adopt a helmet logo, next to the Los Angeles Rams. In 1954, the Eagle wings first appeared on the helmet. The shell remained kelly green and the wings were silver with no outline."

Baltimore Colts Helmet 1954 - 1955 Navy helmet, white stripe and two white horseshoes in back with grey facemask

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