Daryl,
I have "British Handloading Cartridge Tools" by D.J. Baker. Self-published in 2003. I picked it up on a trip to the UK years ago.
I looked thru it for something similar. The closest was this tool.
"A cartridge closer with a jointed hand lever" by G. & J.W. Hawksley, Carver Street, Sheffield, registered design 5586 of 1874
The description is: A pair of tongs have been adapted to create an annular groove in a cartridge case in such a position that the over-shot card is held in place.
The drawing does not have a spring. Your tool may have been an improvement.
So it is a crimper, most likely for thin brass hulls, or maybe paper.
Trulock and Harris had a totally different crimper, but the instructions seem to apply to your tool.
"when pressing the lever against the cartridge, this is turned round until a dent is made above the wad"
Good Rabbit hole to run down.
All Best,
Joe in Charlotte
