House flag of S.A. de Navigation à Vapeur Escaut et Durme
Quoting Mario Boone's scripophily website:
The company offered shipping services by steam or sail from Antwerp to Hamme and other places on the Scheldt and its tributaries.
The company seat was Hamme, Escaut being the French name of the river Scheldt and the Durme one of its tributaries. The share offered by Boone was released on 1 May 1911.
As seen on the aforementioned share, the house flag of the company is green with a white Greek cross.