yunomi-looking bowl and matching spoon, S mark shell mark spiral mark

This is a real oddity.  A yunomi-sized cup thrown and altered to produce a square top rim, with the base partially flattened so that it stands at a 45-degree angle.  A matching spoon with a shell-impressed bowl.  All nicely made and covered with a light shino-type glaze.   It'll make an interesting sugar-bowl-cum-conversation-piece, but who made it?  Clearly marked with an impressed spiral beside an S in a diamond-shape.  The closest spirals I can find in the book are Gilles le Corre and Gordon Menzies, but I don't really think it's either of them.  

I thought it would be an easy one but I'm not finding it. Could by foreign. US or Australian ?

Maybe Julian King-Salter? He had an early spiral mark in 83-87 but my copy of the BSPM mark doesn't show him with just an S mark

Thanks Naomi. I don't think it's Julian King-Salter - different kind of weirdness! I'll see if anyone on the Facebook group has any ideas.

Gordon Menzies had a Spiral mark on Iona Pottery, plus Mike Labrum, but still no idea why there's an S

I see we've been through a similar train of thought before:  https://www.20thcenturyforum.com/t9638-bottle-vase-spiral-mark-gordon-menzies-iona-pottery
The clay in my pot is very similar, and it was bought in Edinburgh, so I guess Gordon Menzies is the best candidate.  Thanks again Naomi.