cut, slab-sided bottle designs occur uncommonly in the world of decanters - a few appear in the first third of C19 in the form of hyalith and lithyalin (Bohemia), then mid C19 rich cutting and ornate designs, followed by art nouveau, and plain bottles with large flat-cut areas seem to only re-appear with art deco, 1920 - 35.
C20 deco chunky angular designs are fairly common on liqueur sets and full sized decanters - possibly more from the Continent than the U.K. Moser and others dabbled, so did Barnaby Powell with a tapering square-section pyramidal bottle that had the name of 'Govette'.
This one is deceptive in appearance - first glance it appears to remain simply as it left the mould - but all of the six sides are cut/polished and there's a large shallow pontil depression - the inside of the neck has been ground/polished though unfortunately the stopper is missing - plenty of base wear appropriate for getting on for a century in age, and one or two small white stones/seeds.
There's no doubting its origin was somewhere on the Continent - possibly Bohemia - as can be seen from the matching No. which looks to be a 41 - but correct me please if I'm wrong - otherwise unmarked.
Height is c. 24 cms (9.5 inches). Quite why the opposing, slightly deformed marks to the lip - I've no idea - could be the remnants of mould seams. They're not damage marks - certainly moulded into the rim.
Almost certainly a dead end in terms of a maker, but thought folk might like to see this as we get few bottles in this deco appearance - but fire away with comments if anyone has more info - sorry the pix aren't too clever.