Newbie Sport Nautique Questions

I just became the owner of a 1997 Sport Nautique and was curious about the little removable seat that sits in the walkthrough space to the bow. Behind the seat on the carpeted walkthrough there are 4 holes in the carpet, what are / were these holes for? The little removable seat has no way to fasten it in place, is this normal? Is this seat even a factory item? The guy who sold me the boat said the entire interior was all original, but that walkthrough seat doesn't exactly match.