Ken,
Dating your 1SU60N can be found in the first four digits of the Serial Number.
5624 equates to the 24th week of 1956, which would be June 11-15, 1956.
I just love the beautiful Robin's Egg Blue Tub interior. In my opinion, it is the most striking of all of the tub colors that G.E. used.
I too have a 1SU60N in my collection, built just two weeks before yours (5622).
I have a poorly scanned copy of the Operating Instructions booklet for the 1SU60N, but I am concerned that the image quality will degrade if I scan this copy. I will try to find who has the original and get it scanned properly to get to you.
I hope you will enjoy this great dishwasher.
Mike