Tenmoku Glazed Bowl With Shell Impressions Incised AB or NB mark

Good afternoon everyone, hope you are all safe and healthy. I picked up this lovely bowl a few days ago from a charity shop whee it had literally just came out of a bag of donations along with some other iems including St.Ives, Upchurch amongst others. Tenmoku glaze is not usually something which appeals to me but I was drawn to this by the impressed ammonite fossil pattern to the rim. The base has an incised mark to which I think reads AB(possibly NB) although none of the AB marks I can find are incised in this way, I have taken an impression with blue tack and drawn over the result with a pen to highlight the letters.

Might be a date after the letters. '75?

I thought that initially also Naomi but there when I pressed the blue tak into that area there was no impression so maybe just the way the glaze has taken making it look a bit like a 7 and a 5?

Looks typically 70s so I suspect it's a date. There also looks like a word beginning with S across the middle; Possibly ST and then another word. Might be a place name.

I agree that it's 70's and that there is possibly a 75, although again this does not show up with blue tak, I do not agree about there being another work there though lol. I see what you mean but looking at it in real life I think that is just ripples in the glaze.

Could that top capital letter be a lopsided M? The sort of thing you might do when you are incising something quickly?