Kudos for picking up on old threads, Nic.
I can't believe I had nothing to say on this the first time round. Hmmm
The cannister / jar.
I have seen these or very similar quite a few times though not frequently, mostly cased over white, though not always. They are usually attr as Italian and nearly always Ponti (Gio Ponti) is mentioned or attributed. Italian is a very reasonable guesstimate. The Ponti connection appears so consistently that I began to give it credence but if you want to be accurate then it has to be viewed sceptically as I have never seen one attribution with book references. I have looked thru my own Murano books just to make sure and nothing.
Gio Ponti one of those magical names in the world of design and architecture. He did design for 3 Murano firms: SALIR, CSP-AVM and of course Venini and did a lot of work in interior design generally. In Murano books his multicoloured striped vases and decanters are usually the pieces shown. In Jackson's list of items he designed for Venini there's no mention of jars or containers.
The quality of the ones I've seen is generally good to high. The cased ones are generally more desirable. There are many variations on the general shape. Other stoppers to appear but the large ball is the iconic shape and is most frequently associated with Ponti. Large hollow ball stoppers do appear on a number of Italian items.
Pete