According to <<https://my.strathspey.org/dd/issue/3201/|issue 3201>> this is in fact the tune the RSCDS published as the "own tune" for the dance <<ddd:Lady Baird's Reel#3589>>. As mentioned in that issue there are several other tunes with "Lady Baird" in the name but none of them are the one assigned to the dance in Book 18.

To ensure it comes up in searches "Lady Baird's Reel (own tune)" is added as an alias.