Strange 1" pipe coming up into stovepipe

[Plarson]

I have enjoyed a lot of the information in this forum, and I'm curious if someone can give me a little more.

A buddy of mine dropped off a stove for me to use at my new place, and it has a 1" pipe coming up from the back and running right up out the center going up about 3'. I was told that it had something to do with the flue, but I don't know how. Another buddy has the same stove, but no such pipe at all!

It is an Earth Stove 100, from what I can tell, and it has knob to open and close an intake in the back.

Does anyone know what this is for and what I should do with it, if anything?

 

[begreen]

Periscope?

 

[ian105]

Home made hot water loop? Where does the bottom part go? Does it look factory? Hard to tell without it being cleaned up