Wolfgang - enjoyed reading about your "project". For what it is worth, I have a '58 Remington marked "Richland Arms" as well. It is brass framed and looks identical to yours - well, almost. Mine belonged to a friend of mine who got me in to shooting NSSA many years ago. He passed away and his widow gave it to me as a keepsake. Unfortunately, the loading lever assembly was missing. I am dating the revolver to the early sixties as that was the time of my friend taking me shooting and I remember we fired the revolver then. If I remember correctly, Richland Arms was located in Blissfield, Michigan - not too far away from where I live in Michigan. Mine has a nice set of ivory grips on it. At any rate, the reason I'm responding to your post is to inquire as to what your thoughts are on my "missing" loading lever. I picked up a spare loading lever that went to a Navy Arms '58 Remy and it was nowhere close to fitting. (of course!) From your statements, you seem to think it is a Pietta make? I don't have access to a Pietta '58 Remy Army (I have the smaller Navy 36). Could you take a "look see" at this revolver and see if you think a Pietta loading lever would work? Many thanks.
(I'm in AZ for the winter and my pistol is in the safe back in MI so I don't have access to it right now)