The long boxes strapped to her chest are holding shotgun speed loaders made by Ignition Custom Engineering of Australia, painted tac-black rather than the jaunty red and yellow they come in from the manufacturer. I have no idea why the artist paired an antique pump-action shotgun designed for trench warfare with some obscure speedloaders designed for Adler lever-action shotguns in IPSC competitions.

She appears to have modified the 1897 to incorporate the new Ignition loading gate that's required for the loaders to seat in place (which is absolute sacrilege to do to a genuine trench gun), although the gate is smaller than it should be, is installed too far back on the gun and is back to front. To cap it all off, she'll find out once she tries to do a reload that the loader holds 6 cartridges but the Winchester's magazine only holds 5.