이셨는데

was ... but, were ... but

→ 이다

이 to be + 셨 Honorific past tense + 는데 Background/contrast connective

auxiliary · elevated, past tense Rare #26,456

was ... but, were ... but A respectful form used when speaking about someone of higher status or showing respect; it often introduces background or contrast.

KO: 그분은 의사이셨는데 지금은 은퇴하셨어요.

EN: They were a doctor, but they’re retired now.

Conjugation of 이다

좋은 분 이셨는데.

They were a good person, though.

— 조조 래빗 (2019)

넷째 마님 이셨는데

She was the fourth wife, though.

— 홍등 (1991)