Thought you would be interested in this STOOF goldmine. I found these S2's in 2008
at Marsh Aviation in Mesa, Az. They are real S2F's. and a lot of them are intact with the  electronics aboard. There were about a dozen of them and I have some Bureau numbers:
> 136724
> 136737
> 136666
> 136743
> 136668
> 136470
Sure brought back some memories thinking that I could have been flying in one of them with Elmer Beardshall and John Dabbs in 1963 and 1964