Castle Pottery coffee pot ??? ("M" mark)

I am wondering if it could be a Castle Pottery coffee pot in this tm listing:

http://www.trademe.co.nz/Crafts/Pottery-ceramics/auction-857832966.htm

The photograph shows identically shaped mugs left and right, a different third mug centre and coffee pot at back, all in the same glaze. The two outer mugs are the same shape as Castle mugs seen on tm and also on the forum:

https://www.newzealandpottery.net/t4910-castle-pottery-mug#18002

Here's Kat's one.

Photo by Kat & Co.

I have asked the seller if there are any makers' marks.

I have also compared it to all the other commercial pottery coffee pots I can find and have found no matches.

I show some other mugs in the same Castle shape but unmarked here:
https://www.newzealandpottery.net/t5693-castle-pottery-closed-down-35-years-ago#21766

---------
16/3/15

Edits for Seller's reply:
"Hi Tnx for the Q, yes the letter M is light on the bottom of the mugs"

I'm wondering now if this is a Hobby set.