Folks, I am overwhelmed by your kind responses, your amazing quick answers and above all, your expertise. Thank you. Sorry... I meant to say THANK YOU.
I've tried taking more close up pix and I think they are more illegible than the ones here. This mark sadly is just as blurry on the wall vase. Perhaps this description might help.
The letter on the centre left of the circle is certainly a "+" (plus sign) and I think also in the same place in centre right of the circle
The first two letters on the bottom of the circle is definitely a "P" followed by either a "H" or could be "M". I'd say the word is about 5 or 6 letters long.
The word in the top circle starts definitely with a "T" and is about 6 or 7 letters long.
The glaze has a satin or semi-matt finish. It's not glossy or shiny if thats any help...