Strictly my personal opinion & granted its narrow in scope. When I think of Auguste Jean I think (1) signature, (2) enameling inspired by Japanese style, (3) metallic treatment for which he held patents. The applied lizard/snakes stuff could have been done by others. Its like the everything is Loetz deal ignoring Kralik, Rindskopf, etc. although you have included Harrach so I my opinion will not help one way or another. I have in the past year found two applied lizard vases in the same colors used by Jean & both were being sold as Jean, Amethyst W/Blue & smokey gray W/Blue, both enameled but not in the Japanese style. One carried the Harrach propeller mark & the other had of all things a very aged faded brown partial paper label (I was stunned it survived even in the condition it was) where I could just make out Bohemia & nothing else.