Halama is at Zelezný Brod so that would have been ZBS in the Communist era, I believe.
I was under the impression that this type of item was first produced pre WWII.
It sounds like František Halama's family have been involved for some generations http://www.halama-glass.cz/
Given that molds were "returned" (to him presumably) in the "restitution procedure after 1989" I think it's reasonable to surmize that his family were, at least part, owners of the entreprise pre 1945. Perhaps Marcus can confirm.
Della. there could be several explanations as to how it turned up in UK.
1) Importation of soap and container from Holland
2) Use of the container by UK soap makers.
3) Import of the container only direct from Czechoslovakia