I don't really think this topic fits in the "Music" bin here, but I don't know where else to park it.
I pulled a partial set of Victor's Marconi Wireless Telegraph training disks out of a box of new records the other day.
Ref: viewtopic.php?f=3&t=55840
Here is what the full set of disks in their box and with their manual would have looked like: https://www.worthpoint.com/worthopedia/ ... -119167438
These records/sets are seemingly of some interest to a small number of collectors. Someone seems to have paid £5.95 for a single disk--one bid only on the disk.
Ref: https://www.ebay.co.uk/itm/325624208005 ... olid=10049
Prior to finding the partial set, I had not realised that such disks existed. But they were definitely a thing. A number of different labels offered similar training sets.
Norman Field documents some sets: http://normanfield.com/index.php/morse/
He also provides copies of the manuals for some: http://normanfield.com/index.php/morse2/
Interesting.