It’s most likely a 5 pin audio DIN cable, used to plug a tape deck into a receiver or similar instead of two RCA pairs.
― assert (matttkkkk), Saturday, 30 April 2022 21:57 (ten months ago) link
5 pin audio DIN seems to be the consensus, most likely for a tape deck
― mark s, Sunday, 1 May 2022 12:45 (ten months ago) link