Sorry but can't help you with the kilt but I am sure that many of the kiltmakers on here will get back to you with their thoughts. (perhaps after the weekend)
It does appear to be a very old kilt and I think those straps may have been original (used as part of the mechanism to keep the kilt on).
It may also help to know the origin of the kilt, if you know it.
Good luck with the mystery
Shoot straight you bastards. Don't make a mess of it. Harry (Breaker) Harbord Morant - Bushveldt Carbineers