Decca 32206, 1967
I've come back to this in part from hearing the remastered CD of The Who Sell Out recently. I've always preferred the sound of the original US single, with its dense mono mix and notably more prominent bass guitar.
Listening to this now, I'm convinced it's a different bass track altogether. On the album mix, John Entwistle stays mostly on the tonic note during the verses, but on the single he follows Pete Townshend's chord changes instead. (Kind of hard to notice the difference with casual listening, especially since the bass line is mixed way down on the album version). It's possible that the the bass on the single may be an overdub, added later to compensate for the poorly recorded original.
Don't bother with the version on the mono The Who Sell Out LP - it's just a reduction of the stereo mix. The single is still the only way to hear this.