Looks like someone tried to add a bit of girth

[Arnot]

Yes, they have added in additional fabric in a different tartan to extend the under apron. Looks like a Black Watch variant or something. It could have been done to make the size bigger. Some old kilts only had buckles on the right side and the under aprons were shorter. The under apron was just tucked into position and was held there when the other buckles were tightened. I have a kilt that was like that originally. I use a slightly longer strap where the seller, or whoever has extended the under apron. The buckles were probably changed when they added the additional strap. The other two would likely have been the old two-prong buckles and would not have matched. They are a pain to deal with as well. In fact, I changed out buckles and straps on a Cameron of Erracht kilt brought to me by a piper from 4th BN, Royal Regiment of Scotland the other week for just this reason. The kilt was old and still had the two-prong buckles.