Interesting. I had noticed that G chord in the final bar of Both Sides the Tweed which seems a little odd to me as the melody ends squarely on the tonic.

I copied the dots from Dick's website but did not copy the chords as I do not play guitar and I normally sing unaccompanied.

For that reason I do not really know what key I sing it in but it could well be Dm as the tune then sits squarely in my vocal range which is a straight baritone being A2 to E4. In fact one tone less than either of the two versions of baritone on the site Don linked to, though when I am well warmed up I can reach G2 but have not successfully gone above E4 - at least to my knowledge.