The name, according to the US Patent/Trademark registration office, was first used in commerce in 1956. It was registered as a trademark by Brownell's in 1982. (
http://tmsearch.uspto.gov/bin/showfield ... vj48zz.3.2). Once trademarked, it included the registration symbol.
Thus, some guesses. The rod, with letter-based line descriptors of the 1960s or earlier, is older than the decal, which appears to have the trademark symbol, and if so, would be from Brownell's, 1982 or later. Probably the trademark decal was supplied with the Brownell's kits or to gunsmiths who specialized in its use on custom products. Some form of the product may have been used in refinishing the rod--80s or later--and the decal applied at that time.