attractive bottle, I like it......... sorry but can't offer anything of use though. The decoration looks good quality - am I seeing some of the enamel colours picked out in gold, and is the enamel thick? Looks like I can see some wheel engraving toward the bottom of the body. Unfortunately, you don't give the height, so difficult to make assessment of its possibly use, although if it were in the range of 3" - 5" I'd suggest possibly a dressing table item that might have contained something like cologne or similar.
The degree of wear suggests substantial age, although it might have had a rough life which could accelerate the visible wear. Assume the second pic is showing a pontil depression with the No. 21. Did wonder if this was a 'matching No.' for the stopper and body - have a look to see if the stopper carries anything similar - otherwise it's probably just a factory pattern/design No.
I could be very wrong, but would suggest European Continental - quite possibly Bohemian or French, and from somewhere between 1880 and 1920. Would like to hear more about the possible engraving.