I have a Griffin & Howe high wall with the same .25 Roberts marking.
Your barrel with the A. O. Niedner, Malden, Mass markings predates the formation of Niedner Rifle Company in Dowagiac, Mich. I believe all of them are pre WW1. How was the extractor for a rimless cartridge set up on your highwall?
I have a few rifles that are so marked. One is a mid range Borchardt with .25 Krag barrel that Michael commented on while visiting. Another is a 1903 Springfield converted to .22 LR single shot - one of about a dozen he did before WW1.
