The tank in the photo is a steel tank. The 3AA designates it as such.
Your photo cut off what the tank valve opening looks like. If it's one of the Thermo Pro DIN/K convertible tank valves, the used tank valve alone is worth $30-$35. The valve service pressure shows 3442, but this doesn't necessarily imply that the tank is rated for that pressure. This is an important distinction.
It looks like the last hydro was in 2004, so you'll have to pay for a new hydro. That can run $12-$25. If there's any rust inside, it'll have to be tumbled (another $25).
The photo doesn't show all of the markings around the collar of the tank. IMO, the most important number would be the end of that top first line. The photo cuts this number off. I see "225" which could actually be short for "2250." That would imply a service pressure of 2250 psi (low pressure tank). It could be a LP72 tank.
I'd ask to see a photo of all the markings around the collar of the tank. It's very important to find out the capacity and service pressure of the tank. That would really go a long way to figuring out its value.
Hope this info helps...