Thanks to Hans van Oost for mentioning the information of Leon Honorez
about Charles Anciaume.  Now, I want to add the following (for what
it's worth):

Stephane Godfroid, who wrote a book about instrument makers from
Grammont, doesn't mention Anciaume as an organ builder; he does list
him in his general catalogue of Belgian manufacturers and resellers
of mechanical music instruments, but he clearly has doubts about this.

Godfroid refers to the same information by Honorez that Anciaume might
have worked at Grammont: "If this is the case, he might have worked at
the Hooghuys factory", Godfroid says, "but this is very speculative."

In any case, the city archives of Grammont don't contain any documents
mentioning an Anciaume as an organ builder, and there isn't any
evidence in the Hooghuys archives that there ever worked an Anciaume at
the factory.  So, to be honest, I doubt that the Anciaume organ owned
by Vincken was built at Grammont.  As I mentioned in an earlier post,
a lot of organs on the invoice list of Hooghuys are from French origin,
so the Anciaume organ could have been as well.

Anyway: many thanks to everyone for the information !

Best wishes,

Bjorn Isebaert
Zottegem, Belgium