gasket placement for overflow box with back

[gregzz4]

My through-glass overflow box uses 1 gasket inside the tank and 1 outside the tank, and both go between the plastic and glass. Any water that may leak past the threads just travels past the gaskets into the box.
And the lock nut is inside the outer box.

Not mine, but same idea
https://i0.wp.com/synergyreef.com/wp...fit=1000%2C442

[corpusse]

One gasket between the overflow box and the the inside of the tank and one between the flange and the inside of the overflow box seems to = no leaks.

I thought about upgrading to a nicer overflow box like the one you've pictured vs the dated design I'm using but this is just a simple fish only tank that less a few elbows and one new bulkhead I managed to plumb together with parts I had in various boxes of junk that are finally getting used.