I am no expert on Limoges, but my understanding is that P M de Mavaleix started his porcelain business in 1908 and operated from then to 1914, when he closed the factory owing to the war. He used M de M as a backstamp. In 1920 he re-opened the factory in partnership with J Granger and they operated as Mavaleix & Granger using the MG monogram backstamp. In 1922 J Granger became the sole proprietor and the company was J Granger & Co from then until 1938, when the factory closed, although one source says until 1950. It seems that Granger continued using Mavaleix & Granger as the trade name for his porcelain and continued the use of the MG monogram backstamp.
I do not think there is any significance in the minor variations in the monogram. Most sources show the bottom of the middle of the M as rounded, but that may be because they have all copied the mark from when it was shown in print for the first time. I have seen a version of the mark, where that part of the M is a definite V shape and you have the "diamond" version. The backstamp would have been re-engraved from time to time and more than one version could have been in use at the same time.
I am certain as one can be that you have the right maker and 1920s as the likely date of manufacture.
Back to: Transferware Collectors Club Website