Overflow question

[LeJeune981]

Just picked ked up this 90 gallon tank with overflow.. But it looks like something is missing.. Can anyone tell me what goes here? Looks like something should slide on this pipe.. There is 2 O-rings on pipe

 

[Pond Boy]

Look's to me like it's for adjusting the water level in the overflow.. More pics of the whole overflow would help..

 

[LeJeune981]

Will do.. Tomorrow after work