[Arran]

 I see, a little more complex, probably smoother action as well, so long as the rubber tires are good. One common fault I see in many of these Philco dial drives is that the have the control shaft routed through a hole in an 3/32'' to 1/8'' steel bracket without any bearing or bushing, it may not matter in the 16 but the older ones sometimes get worn in that area,  the old gets elongated and the shaft ends up with a groove. As I mentioned in another thread I don't think that any of these sets, except the top end ones like Capeharts and McMurdos, were intended to be in service more then 20 years. Now they don't build houses to last any longer then about that.
Regards
Arran