Just checked mine, made 3rd qtr of 99 (same sticker as yours). I bought mine new back then. It has a single, black, hard piece of material, about 1/2in wide and 1/8in thick on the safe side. I would not bet on it, but I don't think I added that "seal". However, I think yours may have been added as I don't think I have ever seen one like that on a "safe" before, but I am a long ways from being an expert on things like this.
Does yours have the black seal on the safe side?