From: Patent Tactics, George Brock-Nannestad


Hello,

a correction.

Mike Biel wrote:
............................................  The same is true of the Mad
> Magazine discs mentioned earlier.  They were cardboard.  

No, the puzzle record from 1979 is a 33 1/3 rpm single-sided thin (see below) 
sheet with an ev matrix number. It is called ' The MAD MYSTERY SOUND "It's A 
Super-Spectacular Day" '. I have no ready means to play it, but I seem to 
remember that there were an incredible 10 different endings to the story.

....................................
> 
> 
> I have about 20 issues of the Soviet magazine Horizon which had flexi's
> bound in.  

----- a similar, but I do not know who came first, was Sonorama from France, 
42 monthly issues from October 1958 to July 1962. They are spiral bound, but 
with only 4 turns at the top and bottom, in order that the full 7" flexi 
record can be played flat when you have leafed to the appropriate one.

.............................

.......................  There was Durium, of course, which were cardboard
> with a very sturdy plastic coating.  

Durium was essentially the surface of an Edison Diamond Disc: a layer of 
phenolic on a hefty paper carrier. They were printed by means of rollers like 
a newspaper.

............................
> 
> The EvaTone discs did not get thinner over time.  They sold several
> different thickness of plastic.  It was the customer's choice of how
> thick they would be. 

----- most that I have measured are 15 micrometers thick, even the 
double-sided ones. But I also have a Dutch manufacture of a double-sided that 
uses 30 micrometers. If kept flat they all play flat.

Kind regards,


George