Would this be a 1950's because of the bright green glow? I know, with Murano glass, it can be dated that way.
The Strathearn P3 Sea Urchin cannot be 1950s because Strathearn Glass was not formed until 1964. And these weights have so far only been identified, through catalogue information, as being possibly "pre-1978". Richard More gives a dating of, "Circa for the time being 1965 to 1979" - which seems very reasonale to me, given the lack of more precise evidence.
Regarding UV reactions, lots of glass from lots of periods will glow very bright green under longwave UV. I do not believe it is possible to be sure that a bright green reaction can be used to identify a particular period - of any maker. For example, I have found with weights by Paul Ysart that by using
both longwave and shortwave, the work from his three periods (pre-1963, 1963 to 1969/70, and 1970 to 1979) can be separated. But I have yet to agree with any author or collector that his pre- and post-WWII work can be identified by the former being a very bright green. I feel the same about longwave reactions for such as Murano.
Is there any real evidence that 1950s Murano weights glow a brighter green than those from other periods (before or after)? Anybody actually made an analysis of this using many Murano weights from many periods and many makers?
Here's the UV reactions of my (Green) Sea Urchin:
Longwave (pretty much the same green)
Shortwave (typical bright blue of Scottish [and other] weights using a lead-based mix)
Photos taken with UV lamp to one side of weight at distance of 5cm (2 inch). Ambient incandescent room lighting. Camera tripod-mounted and set to auto functioning, no flash.
By the way, in answer to whether the (presumed) non-Strathearn label should be removed, I'd personally leave it on but make sure that it is described as being an unknown label. It may be that later, somebody may recognise the parts that can be seen, or the general shape, and then a better id of whose label it is may come to light, which could be useful for future reference.