So I had a chance to pull the pan, the shape matches the TH400 outline, so it looks like a TH400! No parts, metal shavings/etc, the pan was clean. The linkage intact/etc.
However, it seemed very low on fluid, and the pickup (as mentioned by kjk990) does not seem to match the exploded diagrams of the TH400 that I have found. The diagrams show a tube and a large rectangular filter.
Th400 or ???
, on Flickr
The attached flickr link shows what I found in the trans. Its "pickup" looks like it was just at the level of the valve body and barely making contact with the fluid? It was inserted into the transmission though, probably in the place where the normal pickup/filter would be.
I am going to see if I can locate a filter tube and filter/etc for a TH400, but, can anyone shed some light on that weird filter I found?