hello Kylie - welcome to the GMB.
your decanter looks to be more decorative than something intended for daily use - this style of enamelled decoration goes back a longish way into the C19, although my thoughts are that yours is more likely to be middle third of the C20 - but I could wrong - others may know better.
The number you mention is something seen often under the base of decanters - sometimes it matches the same number found on the stopper (but unlikely in this case), and it may also simply be a reference to the guy who decorated this piece or to the pattern.
As to origin, I'd suggest Bohemia/Czechoslovakia/Germany - did your Grandmother originate from the Continent of Europe, or did she holiday perhaps in that area?
Not that it will help in this instance, but it can sometimes be useful to provide the height of such pieces.
