silver cigarette case, any info on country & maker pleas

[deadrock]

Can anybody please give me any info on the cigarette case, photo attached. I cannot find which country it comes from, or the maker. The mark is S 800 AD. I've looked through all the lists on this forum (I think) without success, and I'd appreciate any info. It's quite heavy and good quality, I'm guessing early 20th century European.
thanks in anticipation