I had the top down yesterday and see something is missing on the left side, where the door and the body come together.. The photo shows a hole lined with brass or bronze. Looks like plug of some sort used to be there. The right side plug is in place. I didn't remove the right side for a closer look, just in case there is more to it than just a simple plug. Does anyone know what used to be there and what the part number is for a replacement.