@lilminimonka Thanks for the comments Brianna., looking at the image the tap size is 1/2" BSP. we have been metric since 1972 so must be a lot older than that.
What a crystal clear, gorgeous shot, Peter! Looking at it for a while makes you realize what a beautiful array of colours you were able to catch. And no dust spots!! Glad my misfortune resulted in some positive actions for you.