I have a German gun proof dated for 1907 & another 1913. Both also carry Nitro proof correct for their dates. The 1907 gun is a hammerless drilling (maker unmarked) in 16/16/8x58 Sauer & the 1913 one is a Miller & Val Greiss hammer drilling in 16/16/9.3x72R. The hammerless one is unshootable with major flaws, not the least of which is a burst shot bbl on one side & a bulge in the cone area on the other. The rifle would I think be shootable.
Both of these guns also have the number beneath the date showing what number of gun to go through proof it was. As I recall this started anew monthly.
Although not mandatory at the time that 1210 could very well be a proof date.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra