On Pamela's 'Pavillon' site - under trinket sets for England - there is a single image of an uranium example of a smallish perfume flask, which is catalogued as 'International Bottle Company circa 1930'. The Rd. No. for this particular piece (placed in relief on the underside of the container) was presumably only partly legible - since Pamela was unable to show all of the six digits.
I'm unable to comment on whether the manufacturer was International Bottle Co., or not, and haven't a clue as to where Pamela obtained this information, but can add a little to the details already on the pavillon site, as follows:
The full base wording reads.........BRITISH REGD NO. 755481, and at opposing ends of the base are an upper case letter R, and the numeral 6 (or could be a 9?).
Using the Glass Association 'blue book' (for Registration Nos. for March 1908 onwards - page 15), this indicates that the No. was first registered on 11th June 1930 by the Dubarry Perfumery Co. Ltd., U.K.
This company would have been a very well known English name in the world of toilet luxuries and perfumery in the first half of the C20 - they started out, I think, some time around 1908 - although the name ceased officially in the 1960's when they succumbed to a take-over - I understand that their large and imposing premises were (and think they are still) in Hove (West Sussex, U.K.) - adjacent to the railway station.
I dislike nicking too many bits from the internet, and you can read quite a lot about the history of the company, by ex employees etc. on the web - but I did think that the following snippet was rather intriguingly gruesome .............. "One of the many rumours about the place was that Lady Dubarry was found hanging on the top floor towards the Hove Villas end of the building. That was always a particularly cold area even in the summer". Who knows - maybe just apocryphal.
attached is a pic. of my own example in frosted finish, and doubtless the tin screw cap rusted away many years ago. Heitht is approximately 5"/125mm.
Hope Pamela does manage to see this.