I rather thought so.
It's so fresh to be signed in the 50s or earlier. Are there known secretarials that fresh looking?
That's a good point. I kinda thought it looked rather fresh and unusually clear. The "C" looked rather labored to me; like someone was really trying to make it look like a "C" Gable would normally sign.
I don't believe it's a forgery. It was probably better stored than usual. I've seen a number of older signatures that remained bold. Green ink seems to age well.
Although they are hard to find, I like autographs done in green ink. I think Marilyn Monroe often signed in green ink. I once had a JFK in-person autograph in green ink.
Shirley Temple signed a lot in green as a child. Ginger Rogers also liked green ink earlier in her career. Green fountain pen signatures are more common than green ink pen signatures.