Thanks Brian. Very nice helmet. I see why you thinnk the one in Venice may have originally looked like this.
I have seen a picture of a very similar Mamluk helmet in the Topkapi Museum attributed to Khayrbek, the last Mamluk governor of Aleppo, the one who betrayed the
mamluks to the Ottomans and was rewarded by being made Ottoman governor of Egypt after the Ottoman conquest.
Edit: I have just found a picture of that helmet, please excuse the quality, it's a bad photocopy of a very old book. H. R. Robinson has pictures of the same two helmets in his book, he calls this rounded style a
muwa'ama (A very Arabic sounding name) and attributes it to Khayrbek.