I presume this decanter is by Holmegaard. I found a similar example online, just one, with similar decorative embellishments, saying it was made c.1900. My decanter is c.23 cm high, 8 cm square. The stopper seems original, fitting tightly and securely. It's spherical, but with a slight waist at the base. The pontil mark has been ground out and is circular, concave.
Am I on the right lines with attribution and date? Searches on GMB turn up nothing quite the same. Thanks for feedback.
Anton