Cool!!! You have the OD SOS kit. I had a friend of mine back then in 1990 get one of those.
I got my SOS kit in 1989, 100% leather. The side accessory flaps have deteriorated to the point if you even attempt to remove the items, the leather tears.
The newer SOS kits have velcro closure in lieu of the leather slits holding the side accessory flaps down.