Bates Holdfast

[macs_07]

Does anyone have any information on these little padlocks.
Very interesting mechanism and I would be surprised if there wasn't a patent covering it.
Has a barrel and curtain and three sliding "levers".
All have a serial or independent number.
Two are marked - Bates Holdfast London
One is marked - Bates Holdfast Wolverhampton.
The opening side of the shackle enters a round hole between the solid ears.
The pivoting side if the shackle is blocked by the curtain and can only be opened when the curtain has been rotated far enough to line up a cutout in the curtain with an extension on the end of the shackle.

Possibly official use???
Any information gratefully accepted.
Thanks

[macs_07]

forgot the pictures