When developing a new range or pushing an idea, quite a few items would have been made. Each one would have been assessed before the next variation was attempted. If these experimental items were successful enough to sell they went onto the 'glassmakers shelf' in the shop and were sold.
A while ago I had a chance to view a large collection of these items and it was fascinating to see the development of an idea through a number of pieces. I would guess Chris that yours could date back to Orchid and Lilly trials, the label would not be out of place for that anyway (early 1980s).
The following little pin dish does not quite fall into any known range, it also had a triangular black label.
John