Well - I would exclude Edinburgh Crystal: didn't do any millefiori weights, as far as I know, just commissioned them e.g. from Caithness (or later from Murano).
Caithness did several such millefiori miniatures, including a couple of bells, or a Christmas Lantern amongst others - why not a Christmas tree? Most were facetted - but if a design didn't make it into production (and this one looks a bit crude) it may well have ended up unfacetted and marked second (CIIG) in the factory shop.