Re: the tank
I believe that, at the time of the photo, the tank was called a T43E1. They were built in 1953-1954. They were re-classified M103's in April 1956. I have this belief because:
The lettering on the turret says "U. S. Army Ordnance". And there's no star. So I think this was a photo of a tank still in un-assigned service. Hence it's unlikely to have gotten to M103 status. Also, the photo is not a classic railfan type shot. I looks to me very much like an "official" shot of a new-ish tank. And that could explain how the turret got swung around for the shot--something easy to do if you are in the in-crowd.
And thus I would place the photo between 1953 and 1956.