Sea View gauge

[duckbill]

I have a question regarding Sportsways Sea-View gauges. I was replacing one on a hose when the nut on the back of the gauge came loose. The gauge inside the housing also became loose at the same time, so I retightened the works by retightening the nut on the back. I'm wondering how the unit seals internally to exclude water from entering the gauge through the nut on the back. I didn't want to completely disassemble the gauge for analysis by unscrewing the bezel face for fear that it would not easily reseal. Is anyone familiar with their construction?

[Broxton Chuck]

I got mine loose by carelessness once, and gripped the edge of the boss on back, and tightened it right back up. It never leaked ever. It likely has a gasket or o ring mashed in there to keep water out.