An interesting puzzle pot ...

This is a small dish at 9.5cms and is hand made.  It has an intriguing symbol inside and 1906 - 1956 around the symbol.  No makers mark, but there weren't that many potters in 1956.  What does the symbol represent please?  I can see a CAT or a TAC or an ACT or an endless variety of these three letters

Ev, that base looks very like those of Len Castle's wee ashtrays with slip-trail decoration done a couple of years before 1956. The style of unglazed exterior and colourful glaze inside is also reminiscent of those. I wonder if it is his?

Now wouldn't that be exciting !!!!
I haven't held one of Len's pin dishes in my hand, so can only go by photos, but I don't think so as the wall is very concave and Len's look more vertical. Also most of the pics I've seen they have been made using earthenware. Perhaps whoever made it got the idea from Len ?