Found this set of 6 shot glasses in a charity shop the other day.
On the base it appears to say CLAYMER and then a number I can identify a 3 on some and a 6 or 9 on others.
Out of the set of 6 there is not one that clearly says CLAYMER. Most just have a fraction of the word but over the 6 I was able to work it out.
A quick internet search turned up Clayton and Mayers who seem to be connected to Davidson. Actually Google brought me back to yours-truly.
If I read right CLAYMER were one of the first UK producers (?) to mechanise glass production. A little more digging said Claymer started in around 1953. These shot tumblers certainly look that period especially this shade of green. Screen printing on glass also seems to be a Clayton Mayers innovation?
Anyhow, there seemed to be some disagreement about the who-what-when of the Davidson/Clayton Mayers venture and innovation. I hope my little find helps feed some small info in.
Unfortunately the detail on the base of the glasses is too sketchy to capture with my amateur photographic equipment.