Hi Rascal,
Welcome to the Forum.
You're almost there. The first mark is '18' struck sideways, the second, as you're noted is '750', the third is the 'X' (a St. Andrew's Cross), the import mark of the Edinburgh Assay Office, and lastly the date letter which I cannot see clearly, but if 'y' then 1998, but on that I'm not certain at all, a clearer image will hopefully clear that one up.
The 'DJE' mark identifies the importer, Douglas John Ewing ( Douglas John Ewing, Julia Young Ewing, Duncan Francis Morriison Mearns & T. Dunsire t/a DJ Ewing & Co Ltd.).
See:
http://www.925-1000.com/importmarks.htmland:
viewtopic.php?f=38&t=40776Trev.