Please help with silver plated mark

Please help me to understand silver plated mark below. I wish to know what letters ‘AI’ mean as it was used by different makes in Sheffield and London. Does ‘S’ mean the year ?javascript:emoticon(’:lol:’)

“A1” is often used by platers in an attempt to infer a quality product. It has no defined or legal meaning. The “S” probably stands for Sheffield.

Many thanks for the information. How sure you about A1 mark?
I have some books but i did not find anything about this.
Thank you

I am in no doubt whatsoever about the meaning of A1 on electroplate.

there need not be a hope that A1 has any other meaning than a undefined quality mark - standard set by produceres and controlled by noone.