That is, an object without "M1" on its reverse.
Here's another for you Friedrich. I'm convinced it's a bad fake, though with these first patterns I've been suprised a couple of times by apparently genuine examples of types I've never seen. It's just the lack of detail here that is the concern, I do recall a skull of this general form though. Let me know what you think.
I wholeheartly agree with FB. This type of prong would not be found on a skull of this type and age.
I thought so... having said that, if I came across the original example you posted Freidrich, I'd still probably have assumed it was bad. Such tricky things.
I think this is probably a waste of time even asking, but I feel I must. This Zimmermann skull (I'm considering fake by default now) is being sold by the same guy, this one actually caught my eye first, and I think it looks pretty convincing detail-wise. The only thing that raised suspicion with me is the form on the prong attachments on the back, I know they're usually circular but these ones look different still. Can you elaborate as to how to tell this one is fake? I know it's not on topic with this thread as such, but I felt it would be silly to start a new one on it. I've compared it to original examples already and it matches up well to me, worryingly...
P.S. Sorry for the seller's atrocious photos.