I wonder if you could actually fill that tank with something!

I never heard of Hess toys until I moved to the Southeast. They didn't have Hess stations where I grew up and even where I live now in the Carolinas, they aren't that common. I bought some Hess toys for my boys at a station in Charleston a few years ago and they were really good quality. It was a flatbed with a helicopter. Theirs have been lovingly played with (i.e. totally trashed) as good toys should be, but this is how they looked when they were new:

Yep, the lights worked and so did the rotor on the helicopter!