Silver Ingot Markings

Hi

Can anyone help me with these markings:

AS
Maybe a thistle or flower?
Lion
C or E
Queens Head

My dad says he thinks he bought it for jubilee somewhere in london???

I’ve attached a photo

Thanks
INGOT PHOTO.jpg

This is a Sheffield (Yorkshire rose) hallmark with the date code C for 1977 and the special jubilee commemorative mark for the 25th anniversary of the Queen’s reign. the maker is AS, but I don’t know who this is.