Yes, it is Murano, but it may also be something a little bit more. There are (and were) quality Italian/Venetian glassmaking companies and I'm certain this weight is from one that, sadly, closed its doors last year.
The millefiori design, shape, and structure indicates this is the work of the much lamented firm of 3Fiori, which made excellent paperweights. Study the underside very closely for a hint of a signature, If there is one, it will read 3Fiori. Not every weight was signed, but this could be. You may have to tilt the weight in and out of the light to see the signature.