Jon,
On the broadside titled 'The Maid and Soldier' which = 17 come Sunday the phrase runs 'Her shoes were black, her stockings white, The buckles were of silver'. Perhaps her teeth were buckled!

If you can quote the full verse I might be able to help further. I have at least 85 versions and checking them all would be tedious, and that's without the related 'Brewer Laddie' versions.

Quick glance at half a dozen oral versions shows 'buckles' in all and pretty standard texts showing the influence of the broadsides (numerous printings) which is probably why I haven't done a close study.