64.5 hipo fuel pump ID

The single spring 3734-S is the only one that I have observed for a screw together pump. I did receive a 3734-S pump from Jim Cowles with a broken rocker arm that was setup with dual springs. The arm was broken off beyond where the rocker arm stamping was supposed to be, so I was unable to determine the origin of that rocker arm. The first true dual spring Hipo 289 pump that I have personally observed was an August 6, 1964 dated 3939-S crimp together type. I did restore an ink stamped C5OE crimp together pump that I consider to be a prototype as it had a slight difference in the casting where the plug for the inner spring was installed. I did restore a late July 1964 3911-S standard crimp together pump that I also consider to be in that same prototype category. I would need to check my log book for the exact date but I am not where my log book is at the moment.

-Fred-