I'm relatively new to the study of duobles in general and specifically hammer doubles. But I see that the older doubles generally had tall hammers with spurs that leaned in to place them close together. The later designed doubles have shorter and lower hammers that can only be cocked one at a time. I'm not sure what to make of this. Was the evolution just a fashion change? Was it considered safer to have low hammers? Was the tall hammers considered an obstruction to visibility?