remove tub drain for crane bath tub

I am trying to remove a crane bath tub (installed in 1987) for some renos, but I can't figure out how to detach the bottom drain. The overflow was easy, but the bottom drain doesn't seem to pull out or screw out. It is all walled in, so I can't get underneath it.

There are two photo attachments (from the bottom and top).

Any ideas would be greatly appreciated!

Your pics may have been too big, and failed to attach. Think the max size is about 50K. Try decreasing the res (not necessarily the size) and try again.

drain

It unscrews. but not always "willingly". Sometimes it has to be forced and in other cases it has to be cut out.