Very unlikely that you'll ever find the maker - this set might have originated from one of several countries, including Britain.
As to age - decanters of this shape are often described as 'amphora' (Greek revival, apparently) - quite a popular second half Victorian design which ran on into the art nouveau period, and might be anywhere from 1860 to 1915 - so quite a long run. The trefoil pourer and this type of foot are features that often accompany this design. Of course that's not to say it couldn't be a later copy, but from what you say it does look to be probably from that period.
I'd suggest that the small bit on the top of the stopper is a nipple rather than a dimple - one sticks out the other goes in

- this is also a feature of these pieces.
It's just possible that the degree of wear might indicate the extent of age, but not guaranteed.
Good find and the fact that you have matching Nos. is a good sign of quality and might help to confirm age - sometimes the sort of font/style of matching No. can help with dating and it's also possible to detect a Continental No. as opposed to one from this side of the water, from their appearance.
Sorry this isn't very specific, but decanters can be very difficult to pin down, often
