A real Trowie Tune this one and possible candidate for the finest Shetland reel never played.
The earliest source I can find for this is the 1973 Shetland Fiddle Music LP from the School of Scottish Studies (https://thesession.org/recordings/666) where Gibbie Gray of Unst pairs it with ‘The lass that made the bed for me’ (https://thesession.org/tunes/4034). The liner notes to that disc state that, "Neither of these two tunes can be traced elsewhere".
I’ve added a transcription of Gibbie Gray’s playing on the original School of Scottish Studies recording. Although this LP was released the recordings were made (if I recall the sleeve notes correctly) from 1955.