This blog investigates: History of the DBF insignia

The DBF Pin

In 1969, in one of those heated discussions on who is superior - diesel vs nukes- someone on the USS Barbel suggested that there should be a pin specifically for the diesel submarines who have to fill in for a nuclear submarine because it needed to be repaired. So, there was a contest to commission a design of the pin. ETR3(SS) Leon Figurido had the winning design. When the Barbel was docked in Yokosuka, the pins were made and sold at cost. Now, you decide which
source of information to read: wikipedia and/or submarine sailor.com . I like submarinesailor.com's version.