What is this?

[2233]

Can someone tell me what the function of this metal pipe next to the bathtub is? The top comes off and stuff can fall inside. Also, the tub itself doesn't have an overflow and by using a snake it's apparent the tub drain connects to this metal pipe off to the side.

thanks!

 

[bbp]

old school tub stopper,vintage.

 

[Diehard]

It's called a "standing waste". (Unless there are different types.) And it appears that the overflow you're missing is located within the tube.