I had a Powertree demo sold it privately for £300. a couple of year's back. POWERTREE DEMO was on 2 white sticker's that met across the top, above the address. Found out later with the kind help from other ss member's that underneath the sticker was a KNOX Issue I had never been brave enough to remove it, but other's had. I read the PT demo was a world one off - thank god it turned out not to be so, as I'd already sold mine.
The Knox Issue is the first release, then the intentional Powertree Demo is actually a Knox Issue with a PT demo sticker covering the Knox - then you have the Powertree Issue.
Then I got another surprise - Martyn a ss member told me he was the guy that I'd originally bought my copy from - he found it in a second hand store in U.S.A - he left about a dozen behind.....
Just as a matter of interest and collector's who like me - love foreign stuff - it also came out on Dutch C.N.R and Belgium Cardinal label. If interested Michel Capon, (can't remember correct spelling) from Belgium, (will find his number if your interested) had a copy for sale, though think he'd sold it last time I spoke to him.
Label scan's of each....