I am sure that this botlle is one a group of "unknown maker" items (some paperweights as well as bottles are known). Bob Hall's book, Scottish Paperweights shows a few bottles in the "unknown maker" group.
The examples of the "unknown maker" bottles I have seen all had early Ysart canes and often with some Strathearn canes, too. Also the stoppers showed a clear "tapered" shape and were a loose fit in the neck.
Some looked like copies of Vasart (Ysart Brothers period) bottles with the Ysart style striped neck and well section. Others had clear glass for the neck and well sections. The body shapes varied from "just like older Vasart" to "slimmer / rounder" shapes and often with not much of a neck rim. Often the well section of the body was asymetrical.
All of the ones I am aware of that have been tested under UV light show a blue fluorescence under shortwave uv which is consistent with Vasart Ltd and Strathearn items. However, they do not show the "yellow-green" under longwave uv (blacklight) which is the case (as far as I am aware) for all of Monart, Ysart Brothers, Vasart Ltd and Strathearn.
The lack of yellow-green fluorescence under longwave uv, as well as the differences in variouis visual features, show these to be of a grouo of their own.
No firm date has been put on these "unkniown maker" items but it was proably after Strathearn closed in 1980.