I thought that I would post my two 4 vent M33 I currently own. The first is a front vent the second is a top vent with a what is likely a navy fire brigade (according to another forum example) badge. The front vent is marked S110 and the top vent is marked MM10. Now to track down a 5 and 6 vent. Thanks for looking.

Pair of 4 vent M33Pair of 4 vent M33Pair of 4 vent M33Pair of 4 vent M33