Had another go at trying to identify an "LP" sized disc I picked up
somewhere. I found this reference
http://www.ips.org.uk/audiocompendiu....php?title=MSS

"“Direct Cut Acetate” a system that used a cellulose acetate medium
coated onto an aluminium disc which, though soft enough to cut, was
sufficiently hard to withstand playbacks without excessive wear"
is exactly this description, acetate film over thick Al disc.
It has a small hole on the underside , presumably to drive the disc
around and resist the cutting force.
Unusually this is marked 50RPM, agreeing with the 120 band strobe ring
(uk 50 Hz mains) and you play from the inside to outside, has some
ragtime like piano music on it, well one track anyway, seems to be 2 tracks.
Dated by rubber stamp and endorsing ink, 11 Dec 1944 and AY 1, may have
had another letter beforethe A.
There isa letter D impressed in the aluminium on the underside near the
drive dog hole.
I must get around to taking a recording off this disc by modding a vinyl
record deck to play it properly.
Did the BBC modify their ones to 50 rpm?