I have never seen one.
There IS a drawing on Plate LXI, facing Page 192, Text Book of Small Arms - 1909 of an unusual British Charger. I would assume that this is The Beast.
The Charger shown has the 4 slots in the back, as with the Mark II, but the ends of the back are CONVEX rather than CONCAVE.
As well, it has two LONG oval slots followed by a SHORT oval slot in the upstanding SIDE.
The TOP EDGE of the upstanding Side is QUARTER-ROUNDED at both ends and there is a small INDENT at the LEFT end of the upstanding side, on BOTH sides of the Charger. This INDENT is -shaped and at an angle corresponding with the angle of the left-hand Cartridge as it would stand in the loaded Charger.
So that is the Beast that I'm looking for.
It was gone by the time of the Great War, superceded by the Mark II.
I actually need a couple, as I have a pair of SMLE Mark I*** rifles, a 1907 Navy (Enfield) and a 1904 Army (LSA) and would like one for each rifle.