I noticed some grommet differences between my St Vincent frames (and I know they are SV). Some of mine have 3-piece bottom grommet while others have 1-piece. Also one of the earlier versions have no numbers on the side grommets at all. How many versions of SV grommets are out there? I know the part number for 6 piece grommet sets is Z7156. On the grommet there is number 22D 1615 or something like that. What about 4-piece? Where does come from?