Usually the aficionados just call it The Chronomètre Royal.
Maybe you call it simply The 'Georges Croisier' or The 'GC'?
It was from his workshop, probably the designer also.
Check the VC background info
here and advertisment of his company
here and a patent from him
here
Georges Croisier with his company Genevor SA located at Coulouvrenière 40, 1200 Genève, was one of the most respected case makers of the post-war era.
He was also working for other famous names like Patek or IWC and others.
Poinçon de Maître of Genevor SA is 'the key' with the number 5.