Thank you very much for your kind comments!
@Malmalute you win the gold, it is indeed a Lledo diecast brewery cart as you suggested.
I am one of a dwindling species of gamer who doesn't usually play points, but if I did then something like this would probably be about right:
Points including 3 crew (1 Sargent, 1 Constable, 1 special Branch) 67pts
Cart & Gatling gun 25 pts, Crew 42 pts
My thoughts on rules to use this:
Base speed 11" difficult terrain no effect.
Shooting when moving is a -3 modifier. (e.g. If the cart has moved in the movement phase that turn). and the gunner must pass a pluck test first before shooting. If he fails it it is assumed the gun has jammed due to the excess movement or the shots are so way off it isn't worth rolling to see if they hit.
The driver and Sarge are both armed, one with a pistol, the other with a carbine and can use their weapons.
If the gunner is killed, then the Sarge can carry on using the Gattling gun, with a -1 penalty to shooting. If both the gunner and the sarge are killed the special branch constable cannot use the Gattling gun. The crew can dismount the cart, but if he driver does then the cart can't move, and if either one of the gun crew does then the Gattling gun has a -1 shooting penalty. The gun cannot be dismounted.
A WIP shot and pic of hte original cart here plus parts list:y
http://starshipvorenus.wordpress.com/2014/06/05/scotland-yards-horse-driven-gattling-gun/Cheers!