A Request for Assistance

A reader of this blog has sent me a photograph of a coat of arms on an enameled blown glass jar made in Venice circa 1500.  He hoped that I would be able to help him identify the heraldry on the jar.  After searching through all my general armorials and ordinaries (e.g., Rietstap's Armorial Général, Papworth's Ordinary of British Armorials, and the Dictionnaire de Renesse, as well a thumbing through some of my reproduction armorials (the hard way, page by page), I've come up blank.  (I've often said that, when you go trying to trace a particular coat of arms, you just never know what you're going to find.  Sometimes it's a whole lot; sometimes it's nothing.  You just never know when you start out how it's going to end.)

While the jar was made in Venice, it is entirely possible that the arms on it are not Italian, but that it was made for export.  Indeed, the jar was acquired in England.  Hence the broad search through the general armorials and ordinaries.

I told him that I'd been unable to find the coat and asked him if I could post his photograph of them on-line and ask for assistance from the heraldic community, and he gave his permission to do so.  So, in the manner of posting the faces of missing children on milk cartons here in the States ...

Have you seen this coat of arms?

I am assuming that the border around the shield is simply decoration and not a part of the coat of arms. I also searched for it both as Per fess Azure and Argent ... and Argent, on a chief Azure ..., since it could be interpreted either way.  I did find a number of arms in Rietstap that were Per fess azure and argent, in chief an X Or/Argent, where "X" was a crescent, or a label, or mullets, or a leopard/lion passant guardant, or some other charge, but not a cross Argent, plain, formy, or otherwise.

If you recognize this coat of arms, please feel free to post what you know about it (and in what source you found it, please!) in the comments section below.

Thank you all so much!  I know that if we get enough eyes on this, someone will be able to tell us to whom it belongs.