As you are talking to the chap, can he confirm the watch that he was actually shown? He doesn't need to go as far as confirming that it is actually the watch pictured. I'll happily concede that Dennison were, at best, inspired by the Borgel Calatrava style, but the problem remains the size. I've never seen an early fifties West End in larger than 33mm and that's just too small for the one in the picture. Some sort of lead on what he thinks it is could either keep the idea in the frame or exclude it.