It depends on the belt. When and where it was made and from what material. There is undyed from the deep south, iron dyed from everywhere, pigment dyed imported English leather. Iron dyes depending on the skill of the user and quality of materials could be very black or turned brown (sometimes quickly but after 150 years it is common). If you are going to be using modern oil or alcohol dyes then dye the leather very dark brown then top with black shoe polish and oil to get a close copy of the look of iron dye.
