House flag of Zeester
Pêcheries à Vapeur Zeester (Steam Fishing Co. Seastar), based in Ostend, is known by its founder's share, released in 1919.
The house flag of Zeester is shown on the company share as a dark flag with a yellow star charged with a dark "Z". Given that the design seems to show the heraldic hatchment for green (and the improbability of a Belgian fishing company flag resembling that of Belgian Congo), let us suppose that the flag field was indeed green, a sea-related colour, after all. The initial may be black and would have stood out nicely on the yellow star which recalls, but does not illustrate, the company name (in Dutch, "sea star").