I believe there was a period after April 20, 1895 that Berliner 7" discs
were made of rubber. So sayeth PHP and an old article in APM by Mike Sherman.
In a message dated 4/21/2012 7:27:20 P.M. Eastern Daylight Time,
[log in to unmask] writes:
The rubber disc story comes from Gelatt. I have never seen one, and have
never known anyone to encounter one,