Identifying date mark on Silver bangle

I have a beautiful hinged silver bangle which I’ve had for 23 years. It was purchased from an antique shop. It has the lion and anchor but it also has a date stamp which looks exactly like a back-to-front 3. It also says "pat no. 12596(or 8)498(or B) Ltd. Can anyone tell me either about the date stamp or the pat. no. please? Many thanks.

The ‘back to front 3’ could be an E from 1979 (dependent of the shape it sits in - see 1954). The Pat No would be registration mark of the piece I guess.
Hope this helps

I guess you realise the anchor is the Birmingham assay mark?