Considering the fact that this was a cottage industry, and that the new machines were pretty expensive compared to the old tongs, I think there is probably quite a long period in which both systems were used.
Neuwirth's book 'Beads from Gablonz' could be a good place to get more specific info. There are lots of pages in there with drawings and patents of the machines. Also, I think there are 'in between techniques' which may have given a conical hole, but may also have given a straight hole.
When asking around at the current producers, I asked about the machines. Two of them told me that the machines they are working on now were the machines that are about 100 years old. To give you an idea....
To make it more confusing.....when I visited Neugablonz, where they only started making beads after WWII, there were several places that had decorations made up of the old tongs. So either they were still used after WWII, or they took them from elsewhere 'for fun'.
