Another question on gas tank

[JoeKan]

Hello all,
Last year I was going to replace my gas tank on my 72 burb, but then decided to keep it all original and have the existing tank to be re-lined.
Here's the situation. I have 2 gas tanks. One tank, I am assuming is a reserve tank because it is smaller and I have a valve in the cab which leads me to believe it the switch from one tank to the other.
I was talking to the guy who is going to re-line my tanks and he said he has never heard of a 72 burb with 2 tanks on it before. This leads me to believe that maybe that 2nd tank has been an add-on.
Can you all chime in and let me know if you have 1 or 2 tanks on your burbs please? I've seen the picts of some of yours and there is only one tank.
Thanks so much for your input.
Joe