Nothing to do with Airways Cymru but the Romanians also built a single short body Rombac 1-11, designated 487.
AFAIK she remained on the Romanian register and also saw service with Anglo Cargo Airlines.
I sometimes wonder quite how hard British Midland looked for additional jets, let alone DC9s, when it transpired they were going to be short for the winter 1985/86 season. Airways Cymru probably thought all their Christmases had come at once when BM came knocking!