This is an excellent and healthy tanto from one of the Sukesada from the Osafune school in Bizen, working during the Tensho period. In this case, the blade is specifically dated to Tensho 4 (1576, the eighth month). The Sue-Bizen smiths were known to produce high quality works in moroba-zukuri, and his is a fine example. The jihada is a tight itame and the hamon is suguha with ashi. Here are a few options among the Tensho jidai Sukesada.

SUKESADA (祐定), Tenshō (天正, 1573-1592), Bizen – “Bizen no Kuni Osafune Yosōzaemon no Jō Sukesada” (備前国長船与三左衛門尉祐定), third son of the 1st gen. Yosōzaemon Sukesada, it is said that he signed first with Sukemitsu (祐光)

SUKESADA (祐定), 2nd gen. Hikobei, Tenbun (天文, 1532-1555), Bizen – “Bizen no Kuni-jū Osafune Hikobei no Jō Sukesada” (備前国住長船彦兵衛尉祐定), “Bizen no Kuni-jū Osafune Sukesada” (備前国住長船祐定), son of the 1st gen. Hikobei, first name Hikobei (彦兵衛) too, he signed first with Sukeie (祐家) and bore the first name Hikozaburō (彦三郎) at that time, i.e. before succeeding as 2nd gen. Hikobei Sukesada, he had no heir and so he adopted the third son of Genbei Sukesada (源兵衛祐定), koshi-no-hiraita gunome-chōji, suguha, wazamono, jōjō-saku

SUKESADA (祐定), 3rd gen. Hikobei, Tenshō (天正, 1573-1592), Bizen – “Bizen no Kuni-jū Osafune Hikobei no Jō Sukesada Ashū Miyoshi-gun ni oite kore o saku” (備前国住長船彦兵衛尉祐定於阿州三好郡作之, “made by Hikobei no Jō Sukesada from Bizen Osafune in the Miyoshi district of Awa province”), “Ashū Miyoshi-gun Ikeda-jū Ōnishi Hikobei no Jō Sukesada” (阿州三好郡池田住大西彦兵衛尉祐定), third son of Genbei Sukesada (源兵衛祐定), he was adopted by the childless 2nd gen. Hikobei Sukesada (彦兵衛祐定) as successor, he worked for Nakamura Ukon (中村右近) who was a retainer of the Hachisuka family (蜂須賀) which ruled Awa´s Tokushima fief (徳島藩)