I will chime in with what little I know. I think the swivels, the buttplate and barrel stamp are Niedner. I do not think the stock was done by Shelhamer even if stippling and forend tip are added later. I also am not sure about the pistol grip cap. I think if Shelhamer made a stock like this he would have sawed it in half and burned it before it left the shop (this is something he did once in a while)

gbehrman