My initial thought was that the first pic was a demonstration board, the sort you see in a wholesaler's showroom to illustrate their range of devices.
I wonder why the Sheraton went to the trouble of labeling the Shucko outlet "European socket" though?
You'd think that Continental visitors in London would recognize what it is without being told. Actually, I just had a thought: Maybe it was to stop ignorant Brits asking what it was for!
I'll lay you 10:1 odds that the "U.S. 110 volts" receptacle is 50Hz as well. Looks as though with it right next to a British outlet they didn't debate ground-up vs. ground-down too much!