5 bowls with same unknown mark

I have 5 of these bowls which all have the same marks but they are each individual in style - so by the same hand.

I think the impressed mark is PD or DP - any thoughts welcome.

They may be glaze test bowls, or by a hobby potter as the PD on the foot rim looks inscribed too, and I'm always suspicious when I find a group of bowls with the same mark in charity shops and Antiques fairs. A bit of a long shot but there's a Paul Dennis in Somerset who uses similar ash glazes, but I'm not sure if he's still potting; his website is down

I asked Paul Dennis and he confirmed they are not his work.