Nice bow, and sorry to say, for you, it is right handed!
Trap is correct on length. These bows were made before AMO. 56" would be length nock to nock.
And yes, 4'10" =58", which is actually tip to tip measured length.
I know, because I made alot of strings for old bows like this.
Since it was probably standing on end in the closet, when stringing, beware there could be a twist in the limb.
Hope you can find or trade for a lefty, to enjoy this great sport.
Good shooting to ya!
Steve