Very wonderful old cast iron bathtub , Chester !
I'd say that it's a premo candidate for a restoration job , which in this case (IMO) , would increase it's value quite a bit .
You may find more info on the foundry/manufacturer/model #'s underneath the bottom of your tub (groan) .
If the enameling is intact (not cracked/broken) that's a big plus that would increase the value even more .
I'm of the opinion that the hardware manufacturer is not the same as the foundry that made your tub (might be wrong , but...) .
If the enamel is intact (here's a generally un-published restorers' tip) it can be restored to it's original lustre by using the rare earth compound cerium oxide (an optical polish) !
Thanks for posting it here !