Hi alasearwax,
My best guess for you would be to contact the Factory Direct Manufacturers listed in post #1 here. If they can’t assist you, they should be a good reference for someone who might be able to assist you.
If it is Talalay latex, it would be consistent through. If it is Dunlop, depending upon the production process, you might be able to tell the variation. If it is a 6" core, the bottom should generally be quite smooth and not slit and have a “skin” on it (like from the sides of the mold if the piece is un-slit) and this would generally be firmer. Larger holes can quite often be indicative of the softer side, depending upon their arrangement. I’ve often found that pressing with a finger along the side of the piece of foam into the foam itself (parallel to the ground) is a good way to detect differences in feel (press in toward the top of the piece on then press in toward the bottom of the piece), as long as not directly influenced by pincore holes.
I’m sorry you’re having a difficult time finding a pillow that you like. While not a focus of this forum, you may wish to take a look at the pillow thread here for some ideas, and perhaps site members can offer up some ideas as well. I’m always amazed by the variety of pillows people use here on the forum.
Phoenix