In the February 1982 Word Ways, Darryl Francis attempted to form words out of the 255 different subsets of letters from the set NEUSTRIA. There were eight gaps in his list; two, SRT and TRN, were filled in the February 1983 Colloquy as placenames in Yugoslavia. After considerable searching, I was able to plug three more holes.
Word Ways: Vol. 17
, Article 4.
Available at: https://digitalcommons.butler.edu/wordways/vol17/iss2/4