If a comprehensive reissue of W.T. Narmour and S.W. Smith has been done, I am not aware of it. There are a few scattered recordings here and there. In 1975, County issued 528 and 529, Traditional Fiddle Music Of Mississippi, volumes 1 and 2. 528 includes Mississippi Breakdown, Carroll County Blues, and Avalon Quick Step. 529 has Captain George Has Your Money Come, Charleston No. 1, and Sweet Milk & Peaches. Sweet Milk & Peaches is on the four CD set Roots N' Blues Retrospective, Columbia 47911, and Carroll County Blues is on the two CD set White Country Blues> Columbia 47466. I recommend both highly.
They recorded 31 pieces between 1928 and 1930, then recut 16 of the most popular in 1934. As far as I know, Narmour and Smith were the first to record the well known Carroll County Blues, in 1929. They were indeed responsible for recommending that their producer listen to their neighbor, John Hurt.
This information gathered from the albums mentioned. Quote from Dave Freeman on County 529: "Without question, Narmour must be ranked as one of the more important fiddlers to the rural American tradition."
I am a long way from being an expert in the field of used instruments, but in numerous conversations with a good friend who is a dealer, it all comes down to demand. There are only a finite number of the classic Martins available, and they are highly prized as well as priced! I am sure there is someone out there who can deal with this in greater depth than I can.