Pearls,etc it is!
Thanks to those who identified my gauge; interesting that beads, pearls and stones (diamonds) are apparently measured in the same way and difficult to see what use or ornament a no 1 pearl would be.
John Flack: I was aware of the French word which, on checking, I see also means bead and howler.
The absence of a maker's name suggests that it may be shop-made.