I'm seeing something in the field to the east of the mint mark. Looks like ^^^ although I don't see where on the obverse design that world have originated from.
I see what you mean. I'd need to see a straight on shot of the coin to determine what it is. Assuming it's a clash, it could be the shield?
The shield is in the right spot, and the way the vertical bars on it meet the edge of it is intriguing given the shape of the marks.
Certainly the UK 5p and 10p and 1 shilling coins no longer legal tender, but very probably not worth anything. The UK 1p and 20p remain legal tender here. Keeping the stuff together in the box will give you some memories for ever.