A tool from the the old "Select Series", Princess Auto. Bought new in 2004, never used it, been in a tool drawer all this time. never had air to it so it's essentially new. Certainly looks to be of high quality.
I measured the punch and it looks to be 3/8, but I see PA has them up to 5/16. Maybe it's 5/16?
It would be a great tool to have if you're doing any sheet metal work or pans.