Hammergun,
I will do my best. We know it has to be 1892 or later because it is a modified diana. So, the rest is elimination. It does not have the diamond / rhombus with the gauge markings, they started using that in 1898. I don't see any indication of nitro proofing.
A lot of the other marks are the old fashion controller of proof marks, for which we have no information. Some of the other marks, eg N in circle, may be from the Pieper factory, indicating job codes or quality control.
How's a 6 year time span, 1892-1898? I have seen ads for the modified diana that were much later, so this is a relatively early gun. I have never seen a serial number list for these guns.
For the diana and modified diana guns, you can be sure the damascus was produced at Pieper's "Brazil works" barrel shop. Probably by some of the people in this picture.
Pete
