Off-metal 1964 Lincoln cent struck on a silver dime planchet, and also with lots of flakes of copper struck into the coin's reverse. The coin is the design of a cent, but has the metal of a silver dime. This error occurred when a silver dime planchet was accidentally fed into a cent press and was struck.
The copper streaks which are seen across this coin's surfaces are from the cent dies that struck it. The dies which strike coins will often get a light coating of the type of metal which they're striking (for cent dies, it would be copper from the copper cent planchets), and for some reason, when those dies then strike coins of another metal (in this case a silver dime planchet) the traces of copper will sometimes stick to that newly struck coin, which is what happened with this coin. This phenomenon is seen on off-metals of all combinations to varying degrees.
PCGS MS-62 with problem-free surfaces and streaks of copper coating the silver dime planchet.