hi, welcome to the GMB.
regret I can't help with an attribution just at the moment, but we may have someone here who will know more about this decanter - there are people who have very good knowledge of marks and backstamps.
However, just to say that my opinion regarding the small quatrefoil shaped mark with loops and small cross, looks to have been sandblasted rather than etched.......... this process is suggested by the lack of sharpness to the edges of the motif, and the grainy/coarse texture - although I'm unsure about the deer and mountains.
Unfortunately, this doesn't really tell us much about your bottle - sandblasting has been around for a very long time. Also worth bearing in mind that this smaller mark may well indicate a wholesale or retailers mark, rather than the maker.
fingers crossed someone will have the answer.