Unfortunately the base finish (or lack of it) does not indicate anything specific to me.
All of the "Ysart" millefiori weights in my collection which show under UV as pre-Vasart Ltd have a look that is different from the general appearance of so many Vasart Ltd items. A main difference is that in Vasart Ltd weights the canes often show as "long" lengths rising above the coloured ground and the canes are usually separated from each other. In Ysart Brothers period (or earlier?) weights, the canes can appear to be "long-ish" but they are not so pronounced as in the Vasart Ltd items and they are also set closer together, apart from a few, such as the occasional "spaced cane" design weight.
It would require a short wave UV check to decide if your weight is, in fact, earlier than Vasart Ltd, but I doubt it is. It could, in theory, be very early Strathearn Glass, but there is no way I know to determine the difference for those!