This single has only two tanks, and we are beginning to think it has two 170-gallon tanks.
Look around on the tank. Usually the tank builder sticks a tag on it with lots of data, including capacity. Tag might be in hard to see place.
I think that's a requirement but it might not have been back then. If the tanks are rectangular, it's a pretty simple task to measure them and figure out the capacity.
There is no requirement to have you deck fill caps marked with the tanks capacity.
You are correct but that's not what I posted. I posted about the tanks themselves, not the deck fill caps. That was someone else.