Hello.
To my knowledge, ARS (Atelier de Rennes ) is the only one manufacturer which produced cases of 65 DEM. I have never seen another. For sure, it is not a proof!
I have not the pictures of my cases but I can show scans of them.
Note that, at first the stamping was ARS 65 Me at 12 o'clock and lot number, year of manufacture, metal supplier at 6 o'clock. Then 65 DEM at 12 o'clock ARS, lot number, year and metal supplier at 6 o'clock.
During the years 1910, 1911, 1912 (partly) ARS used a date with four digits ( as on cases of 75 DEC). Probably in 1912 the L for Lot moved. It was first between the lot number and the year ( as for almost the whole manufactures) and then between ARS and the lot number. On cases of 75DEC made by ARS, this change took place during the year 1908.
Some cases of 65 DEM were, according to regulations, cut down to 110mm to be used as cartridges for a mortar. The majority of them have kept the original stamping but some rare examples are stamped MORTIER at 12 o'clock.( please see the last example on the scan2)
I have also an example with the date 1925, the same year of the primer of your. Perhaps a requirement of cases of 65 DEM appeared this year?
Regards,
Dandebur.
View attachment Scan0001.pdfView attachment Scan0002.pdfView attachment Scan0003.pdf