An interesting pen for Sheaffer fans. Japanese pen giant Sailor made the Sentinel for Sheaffer in the 1980s.
The steel F-4 nib is a dead giveaway, and the sizing follows the Japanese. So while the nib has an “M” on it, it looks more like a Western F or XF.
When I first got it I didn’t notice the engraving on the cap: “AUPE BEST PERFORMANCE BR”.
What’s the AUPE? My guess is that it’s the Amalgamated Union of Public Employees. Ah, irony :p