+ @awemawson
Looks like the left hand side of the tool fit the flange & the right hand has a taper & swivels to close the gap between spot welds when hit, at the same time hitting it helps the movable head to align the edge so flange is straight.
Never seen one either here or in US so I may be talking garbage
Always done it with a flat dolly & shrinking hammer
I'm pretty sure the handle is holding a clip which is being pointlessly fitted to the edge of a spot welded seam, I'll try to find them but dont know what they are called, thought they were a type of cleco but thats coming up with nothing.
fixturing tools are shown holding small metal pieces. Left: locking pliers. Center top: magnets. Center bottom: standard Clecos (left) with both sides shown, and Cleco edge type clamp (right). Install tool is below them. Right top: thumb clamps. Right bottom: pressure-type edge clamps and install tool.