WDE,

The 1210 could be a date but it would be somewhat unusual in that mandatory dating didn't get into common use until about mid 1920s. I have had a couple German guns which post dated this one that still didn't have a date stamp. I would think this gun came in the 1892 -1911 proof laws period. After 1911 Nitro proofs became more common than just black powder proofs. Your gun has no nitro proof marks that I can see from the photos. They would typically show on the side of the barrel and on the frame.