Identify this device.

[LEOlson]

Hello. I am new here. I am trying to figure out something in my attic. This mysterious black box appears to be connected to my attic fan, but it doesn't seem to actually affect anything when I twist the knob. Can anyone help identify it?
Thanks in advance!

 

[James]

Could be a thermostat
sometimes things like that should be dealt with in the following way.

if it ain’t broke, don’t fix it!!

 

[Darkwood]

As above or a humidistat, it may not seem to work because humidity isn't high enough or the temp' is outside the range when you tried it.

 

[LEOlson]

Hiding in the shadow of the knob is the word MINUTES. I didn't realize it was so hard to see until now.

The issue I ultimately want to solve is that my attic fan runs 24/7, even in the dead of winter. It didn't used to, it used to only run when it was hot. I am not going to attempt any wiring work myself. I am just trying to figure out what is up there.