Hmm, I had forgotten that other thread, but this definitely seems to suggest the two almost identical cases, one straight-tapered and one necked were different products, since
@Hoeksel says the straight one has code "73" for Bulgaria and we know the necked one had code "835".
Also, it seems likely Krupp started by having mountain guns with the straight tapered case and then, at one point, switched to the other necked case, possibly to aid in extraction, or for better shell retention, we don't know, because the Romanian document from the 1930s gives the gun that uses this shell casing as "75mm Krupp Mountain gun Md.1914" and also mentions "German" - now that isn't either here nor there, because this doc is very inconsistent wherever they list the country of origin or the country of adoption and you'd see ammunition for the same Krupp gun listed alternatively as "German" and "Romanian" despite the fact the gun designation doesn't change. Also it's debatable wherever we ever adopted this gun before the war started or if it was all from captures during the war - there are a few documents which suggest we might have gone to Krupp in late 1913 after the Second Balkan war and bought whatever they had in stock, but some other which suggest the sale never went through, but whatever the case, this suggests this gun was never specifically made for us.

Oh and another thing, I just talked to
@Irod7 who can't post at the moment as he's travelling for Easter and he says his ground-found case marked "835" comes from Vrancea, where there can't possibly have been any Bulgarians at all - that area of the front was Romanians and Germans only, not even Austro-Hungarians, which seems to suggest even more this was a Krupp export mountain gun used by the Germans which we acquired through capture.
However, this all poses an even bigger problem, which is that Bulgaria switched to Schneider-Canet guns from 1907 onwards which are specifically stated to use the same ammunition as the Krupp M.1904 guns.
So then, when did they acquire a Krupp gun with the necked "835" case?
Because what that says to me is the "835" case simply can't be Bulgarian because they were already using the straight walled tapered one, code "73" and there was no reason to change.
So while "835" is definitely an internal Krupp code for this particular case for mountain guns, there's absolutely no indication this has anything to do with Bulgaria at all, specifically since
@Hoeksel's own paper states that cases marked "835" have popped up as far afield as Spain.
So if anything, this made me think even more strongly that the straight tapered casing with this shell as posted by
@bombista is the proper Bulgarian one, because, again this is the drawing of it from Bulgarian docs - notice no neck and similar shape and fuze, etc.
