Getting off topic, but more info on the G mark! It may be solved.
http://www.silvercollection.it/dictionarydecryptingsilverplatemarks.html
"The marks of electroplated silver were often inspired to the hallmarking used for sterling silver and the maker was identified by its initials inside a series of squares, circles, shields, etc. The effect was apparently similar to sterling silver hallmarks, obtaining the result to gratify the buyer's pride to exhibit a high value object and the unconfessed objective to deceive inexperienced people."
"Usually the initials were in capital letters, often in "Gothic" characters. Less frequently the maker's name was written in full or was represented by a figural trade mark."
Here is a list of many silver plating marks from other manufacturers that started with G:
http://www.silvercollection.it/SILVERPLATEHALLMARKSG.html
After reading this it almost seems like it was not a Government requirement but possibly something Gillette did to increase appeal. But why would they have only done it to their French sets and not all their British sets...
http://www.silvercollection.it/dictionarydecryptingsilverplatemarks.html
"The marks of electroplated silver were often inspired to the hallmarking used for sterling silver and the maker was identified by its initials inside a series of squares, circles, shields, etc. The effect was apparently similar to sterling silver hallmarks, obtaining the result to gratify the buyer's pride to exhibit a high value object and the unconfessed objective to deceive inexperienced people."
"Usually the initials were in capital letters, often in "Gothic" characters. Less frequently the maker's name was written in full or was represented by a figural trade mark."
Here is a list of many silver plating marks from other manufacturers that started with G:
http://www.silvercollection.it/SILVERPLATEHALLMARKSG.html
After reading this it almost seems like it was not a Government requirement but possibly something Gillette did to increase appeal. But why would they have only done it to their French sets and not all their British sets...