These are dictation discs for the Gray Flexograph.
They are constant linear speed and require a special playback machine. When played on an ordinary turntable, they appear to start at one speed and end up at a way different one.
I have the machine and have transferred quite a number of these.
Smolian Sound Studios
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Karl E. Fitzke
Sent: Tuesday, January 05, 2016 3:34 PM
To: [log in to unmask]
Subject: [ARSCLIST] Translucent Blue Plastic Flexi-Discs - What do you know about these?
Happy New Year, everyone.
A fellow Cornell Library employee just asked me what I might know the type of disks they just found a stack of in a box of archival submissions (french lessons?). Short of my experience with cereal box records as a kid and magazine inserts later in life, not much. Here are some photos.
Without looking closely, I'm guessing that they play inside to out, based on the blank material on the outside of some of them. And that the technology enabled multiple but independent tracks, i.e. that don't necessarily play one after the other. The keyed spindle must prevent these lightweight discs from slipping. The few disks I looked at are only one-sided, but there are designations of "1" and "2" cut into them.
Anyone have a machine made to play these? Would it be foolish to try with a standard turntable (after some closer inspection of the groove to make sure it doesn't require the turntable to revolve in the other direction)?
As always, I'm grateful for the community to consult here!