Mateba produced some interesting sets of revolvers, namely the Unica 6, which in H3 is currently only using .357 Magnum, but there exists a super rare .454 Casull version that also has a different barrel and cylinder options to even safely load .45 Long Colt!
The construction of the .454 Casull requires the latch and frame to be reinforced to withstand the pressure from the .454 Casull. Further the whole revolver needs to be slightly extended to accomodate the length and diameter of the catridge.
The revolver takes on hidden rails on each side of the weapon, alongside with muzzle devices/suppressors and also pistol stock.