Picked this up a few months back in a job-lot of glass from Denmark. Have a feeling it might be by Riihimäen, but cannot track it down on Designlasi or similar sites.
The blue is good for the factory, and I know a few designs had bases with concentric circles - but not usually quite so pronounced (as far as I've seen).
It's 165x90mm (HxW), and finished to the top with a cut and chamfered rim.
Any help gratefully received.