I was going to CMP, Anniston when the Krags were available. I saw several with this modification although the brass inserts were secured with screws through the side plate on the ones that I observed. There were two classes of Krags: 1) the ones turned in from VFW's, American Legion Posts, etc. and 2). ones belonging to the movies studios ( MGM, RKO etc, ) that were traded to the CMP for M1903/03-A3 drill rifles that was needed for the TV series South Pacific. The ones from the VFW's, American Legion, etc were, in general, in better condition. I still have my M1898 with 1898 cartouche and M1896 rear sight. I wish I had bought one from RKO. Could have been used by John Wayne or Errol Flynne.

Thanks for the insights.  I clearly have three of the exact blank adapters described by Mallory.