www.925-1000.com

I believe this to be an old Hamburg assay mark. It looks like an "x" is the letter. Can anyone assist with this?

Thank you!

I have seen this X-hallmark with engraving from 1825.
Makers mark looks like [Fencker]
Johann Friedrich Fencker, Gold- und Silberarbeiter/Juwelier
*1780, + before 1839