As to Prior, it was a sub-brand of these folks:
GOC stands for Gros, Grenier, Ostero & Cie., an obsolete brand from Saint-Claude. A GOC sub-brand / second was named Prior.
The name "Gros" also appears in context with a privity named Vincent-Genod, Duparchy & Gros, who bought Comoy-David - Fabrique des Pipes - in 1923. Just one year later the name was Vincent-Genod & Gros Frères. See Genod.
So, more than likely Gros, Grenier, Ostero & Cie. weren't pipemakers but rather wholesalers and perhaps financiers in the pipe and tobacco branch, who had pipes made as private label orders.
Document: Gros-Grenier-Ostorero & Cie factory -- Pipes: Logos & Markings
Don't know what the value would be.