Yes it is threaded. I am sure it is a standard seat belt bolt size same as the other seat belt bolts in the car.
If you really need me to I can look up the bolt size and take some photos but I think you are worrying too much. You can feel the hole quite easily so just put a small cut in the center of it and try a seat belt bolt.
I tell you what. I will take a picture tonight when I get home if it is not raining.