Keith's is VEB Glaswerk Olbernhau/ Dave's could be too
http://lustrousstone.co.uk/cpg/displayimage.php?pid=76
Either VEB (former East Germany) or Flamingo (Holland), but I'd definitely look at the former as the likeliest candidate.
Chance Additions contains the updates to these 'unknown' patterns.
However, since that book was published I have come across another Dutch maker called The White Goose(!) and the triangular dish at the bottom of p.111 (
Additions) is probably from that company - the circular textured plate immediately above this was almost certainly made by it. See the attached photos of a square tray with The White Goose label (thanks to Ivo for contributing this)