The 3" floppy was available in single (flippy) and double-sided.
But, the two different driveswould not accept each other's disks! (You
could not use the flippy disks in the double-sided drive)
Besides the Amstrad, it was advertised and sold for AppleII and Coco,
under the name Amdek in USA, as an external two drive box.
I have heard that it was offered for other systems, but the ads that I saw
were offering only for Coco and Apple
--
Grumpy Ol' Fred cisin(a)xenosoft.com
On Mon, 23 Jan 2023, Adrian Godwin via cctalk wrote:
There was the Amstrad floppy. I think it was 3".
Hopefully didn't get out
of the UK.