How does that air pistol work? Anyone know?

Webley / Webley & Scott battlefield .177 Air pistols For Sale in Dyfed

webley mkv1 service revolver .177
4.4mm bb
built from original blue prints
loads ,cycles,fires and ejects as original.
original 1915 markings
single/double action
full size
full metal
6 inch barrel
6 shot
2.4 lbs