Alan
You won't believe this, but I have just got back into the office after a stroll round town (Rump steak and caramelised red onion baguette - yummy), passed the market and picked up from a stall a very similar weight. Blue base, 6 complex canes at 1, 3, 4, 8, 9, oclock with stencilled PKM at 6 oclock, and a centre with 6 canes round a centre. Slightly flattened, ground out pontil and firepolished, slightly grey glass. . Cannot compare it with yours since work laptop disables hosting sites. Will have another look on wifes laptop tonight
Will put up a picture when I have the chance