You're welcome. Nice looking car.
Since it does have the WS6 RPO code then it is a real WS6 even without the rear badging. What could have happened is that the rear of the car was damaged and when it was fixed the badge just wasn't replaced, one of the people who had it before you just removed the badge for some reason, the adhesive tape that holds the badging on could have lost its adhesion and the badge just fell off. Who knows though since all real/true WS6 cars did come from the factory with the badge.
As far as the 2 98 WS6 convertibles, you really can't count those as production vehicles. Both of those were made by GM as strictly "show" vehicles to introduce the new body style to the public at the auto shows. Once those shows were over those two cars were given to GM emplyees and were never meant to be released to anyone else. One of them is still in the hands of GM but........one has made it into the hands of a non-GM employee and has been that way for several years now. I know that for a fact because two people have owned it since the original person that GM gave it to bought it. Both of those people are here on TFS, one is the first of those two to own it and the other one is the current owner of it.
As for how many were made in 1997, I don't have a full break down between the WS6 verts and the non-WS6 verts but a total of 324 convertible Formulas were made in 1997. So no matter what you've got a fairly rare car so you better take care of it real good.