A signed in the fiftieth session carries a large six-character inscription, Sekishū Dewa Sadatsuna, cut across the second , and it is this rare full signature that anchors the smith. Sadatsuna worked at Izuha in Iwami Province in the late period, and the published sources transmit him as a son of the first-generation Naotsuna, the Sekishū master counted among the pupils of Masamune who carried the tradition into the provinces of the San'in coast. The reference works record the name across three or even four generations descending into the period, the first placed about the Shōhei era, the later hands in Meitoku, Ōei and Kōshō. Because signed pieces survive almost only from after the entry into , and examples dated to the are scarcely encountered, his earliest work is read on the evidence of the and rather than from an inscription, which is why so much of his designated body is and appraised to his hand.
The recurring verdict across his blades is that Sadatsuna resembles Naotsuna while tempering a smaller in scale. His is fundamentally a , present on every one of his designated blades, that runs in linked sequences across the , mixed with and angular , and at times a round-headed and a slight chōji-gokoro. enter, the runs deep, and the adheres strongly, coarsening here and there into rough crystals. Through this temper and work vigorously, with drifting in places, so that the activity within the is conspicuous rather than quiet. The single clearest tell sits in the , which brushes into on most of his blades, sometimes burning out in a manner, sometimes turning back in with a pointed tendency and a long . It is in the point that the inheritance shows most plainly, the swept carrying the temper past the .
The is a standing mixed with and a flowing , the grain opening rather than closing, so that the published sources reach for the word to describe its loose, granular surface. Over it adheres well and often dust-fine, enter, and the steel takes on a kana-iro tone darkened toward black, a provincial Iwami that distinguishes the school from the tighter, brighter of the masters it imitates. On the a -like mottling gathers toward the lower half, and the thickens to a fine dense cover. The whitish cast that marks much wakimono work appears on one early but is not his rule; more typical is the dark, active against which the and of the stand out.
The published sources draw his work into two registers. They state plainly that he is seen both in a -based manner and in a -based manner, and that in either case the adheres well and the is applied vigorously. The manner is the principal one, the linked with its angular and pointed elements and its strong, sometimes coarse . The manner runs a shallow or small into the , the tending to sink toward a subdued , the and drawn out long, and it is carried above all by his , broad and slightly with thick and very shallow . Form follows the late date: the run to standing in a blackish steel, while the one slender, deep-curved, with its two-character signature keeps a classical silhouette that the published commentary calls archaic in feeling even as the -laden temper marks it as Naotsuna's circle.
What places him is the line itself. The published sources name his manner as that of the Sekishū Naotsuna group expressing the Sōshū-den, and an appraisal to Sadatsuna as a follower within Naotsuna's circle is one they say can be accepted for exactly these reasons. Of the first designated they write that strong , frequent and intermixed mean 「相州伝が認められ、直綱に通じるものがある」, that the tradition is recognized and there are points in common with Naotsuna. The smith-level characterization repeated almost verbatim across his blades is 「直綱に似て、互の目調のものと小のたれ調のものを見る」, that he resembles Naotsuna and is seen in and manners alike. He is the school's hand at one remove from its founder, faithful to the idiom but working it smaller, darker and more provincial than the originals, and standing above the Nagahama smiths, Shōmatsu, Shōsada and Rinshō, who are counted as his subsequent line.
Sadatsuna is rated Jō- in the Fujishiro ranking, and eight of his blades hold the rank of -, with no National Treasure or Important Cultural Property among them; his record is that of a sound provincial master, not a great name. A signed of his is called by the published sources 「貞綱の見どころがよくあらわれている」, a piece in which Sadatsuna's points of interest are well brought out, and a fine and forceful example among his works. One of his descends with an written by Kōjō and dated Enpō 7, the year 1679, which attributes it to Sadatsuna and which the modern commentary affirms on the strength of the blackish and the linked of well-adhering . Provenance is otherwise thin, with no houses or museums recorded among his blades, so the honest account is of a body held quietly in private hands. For a collector his work is among the more attainable of the -influenced provincial masters: most of his designated blades sit in the tier rather than locked away as patrimony, and a signed example, fixing the name with certainty, is the rarer and more desirable encounter, coming to light only from time to time and with patience.