[csx700?]

computerworks
1) the photo of the belts that are in the photo with the red seats appear to be brown (natural) not black as you say? they appear to be the correct pieces but if the pad is black i would be suspect as to the leather having been replaced at some point, no copper rivets either? unless the supplier had indeed used a black pad, anything is posible.
2) the secont photo appears to posibly be from a 427 car. the leather is on the opposite side and is black in color.

dan case
you are correect in stating that military hardware was used to make the sert belts. there were many suppliers of th hardware so there could be some variation in the parts supplied to "ray brown" or "impact".