Scupapro regulator from the 1970's. A Mark 7 with a "honker" that made a loud honking noise when tank pressure fell below 300 psi as a warning for low air reserves. Similar to a J valve where breathing became very difficult at 500 psi until a lever was thrown to access the "reserve".

Thank you to Sludge for the additional information. This was originally posted under the sign thread.



Click on image for a really big version...