This is from one of the guys on Seiko/ Citizen section and is the holy grail of info on the Citizen "Bull Head". A really excellent site so well worth posting here for future reference.
Automatic Chronographs | Sweephand's Vintage Citizen Watch Blog
Want An Original Citizen Bullhead? - A Quick Buying Guide | Sweephand's Vintage Citizen Watch Blog
Automatic Chronographs | Sweephand's Vintage Citizen Watch Blog
Want An Original Citizen Bullhead? - A Quick Buying Guide | Sweephand's Vintage Citizen Watch Blog