The ‘68-S and ‘69-S are notorious for this kind of thing. Here’s another ‘68-S. Same thing, extreme strike doubling. Seen one, seen them all.
Back then, the design was pressed into the working die by a hub, which had the date on it. If the die was going to a different mint, the D or S was added by hand with a steel bunch and a mallet. A doubled die would affect the date but not the mint mark. A double punched mint mark would affect the mint mark but not the date. When both the date and the mint mark are doubled the same amount in the same direction, it MUST be machine doubling. (Note: Date were added to hubs starting in 1907-1908. Mint marks were added to hubs around 1985,IIRC.)
Do you understand how this happens? It's caused by a movement of the planchet when it's struck. That's all it is.
That's all caused by the shifting of the planchets when they were struck into the coins. Look up how the cents are minted on YouTube, to get a visual of it. With all that rapid pounding, the collars securing the planchets loosen up some, and the strikes go a little haywire for it. As far as value goes, there's no premium, unless they're really, really, really cool. That's three reallys, note. If it's just two reallys, or one really, forget about it.
my example is really 5x cool. he has a BIG nose and double chin. i have not came across something like this. i'll send to to pro cleaners, slab it and keep it. but will sell if the price is right. i'll take $5k