Really the same, or just similar? All the similar treatments I've seen, by Eisentraut, Cooper, Trek, etc, were only similar. I haven't seen the same treatment anywhere.
Does the pinch bolt thread into the ear on the left side, or is it a two piece bolt? It looks like the former to me, which strikes me as an anachronism. Other than that, I agree with your 1973 date.
Oh, I suppose it's a similar treatment, not identical, but given that I'm mostly comparing to photos of various quality, it's hard to say for sure. As far as that pinch bolt, it's conventional: one piece, threads in from the drive side.