A little story, hopefully to amuse:
I have to say this was remembered from a lesson given to me by that young Patrick Hogan chappie.
Two dealers, both of whom used to be based in Kensington Church Street, assured him his strange vase with horizontal tear drops most certainly couldn't be by Powell........one of them being, well, umm, errr,
Some years later, having found the photos at the Museum of London, Patrick put them up on W/F's dot com. So, I would love to find one to remind me not to be so quick to dismiss things that, particularly in those days, used to turn up from time to time - certainly far more often than now!!
As for the 'S'; given the way it seems to be scratched/incised to the base, it suggests second, so maybe look for the imperfection?