WWTEng:
There were a whole bunch of proprietary systems which looked essentially like that, from that era. Most beams in that era were more like today’s S shapes, as were the Tees of that time, so not likely WT’s. The clay tiles were just dropped onto the Tees dry, and then several inches of concrete, with some reinforcing would be cast on top, and btwn. the tiles, depending upon their upper shapes. The whole floor system acted as some sort of a loose composite system, in two directions, but it had good depth and was relatively light with the clay infill. The best thing to do is find someplace with min. loading, and/or min. slab shear and no slab tension; gently open up a 2 or 3' square area from above, and study what you’ve got as you go down. Maybe try to save the bottom half of the clay tiles. Then fill the hole with light weight concrete.
I’d look in a good local engineering library and see if you could find some old catalogs, or some good old structural engineering textbooks or handbooks. Take a look at SlideRuleEras’s web site, here on E-Tips, he has a bunch of good old stuff on file there. Many of those systems had special tiles which fit around and under the steel, because part of the selling point was fireproof floor system construction. So, in that respect, what you show is a bit unusual.