This appears to be a pair of patches.  I don't want to separate them to preserve the historical context appearing on the same jacket together.  The top patch is for the International Roller Derby League, an derby organization which came to a screeching collapse in 1973 and finally died when Jerry Seltzer sold the rights to Roller Games, a rival league based in Los Angeles.  (Roller Games lasted another two years before it died as well.)

The IRDL peaked in 1972 a game that was a grudge match of sorts between competing organizations when the Los Angeles Thunderbirds (Roller Games) played against the Midwest Pioneers (IRDL) at an event attended by 50,118 people in the audience.  No derby event before or since has reached that level of attendance.

The bottom patch refers to the Bay Bombers, one of the IRDL teams.