Welz vanity covered box

I bought this expensive little box because the base appears to have a pontil mark... but why would the base need a ground pontil if the piece is a simple bubble cut from the top? My best guess is the piece may have had a blemish and was never transferred to the base... so grinding just to clean the piece up.

My second theory was the piece was blown entirely in one piece from the bottom so that the finial could be applied and the center was cut out to allow the piece to fit into each part.