This light grey vase is approximately 158mm (6 1/4") tall. The base is more heart shaped than round and has small evenly spaced bubbles that go horizontally around the ball. It has a very smooth slightly concave bottom. The stem has a narrow flare being approximately 18mm (7/10ths of an inch) in diameter and is the same colour as the base.
The round paper label has a matt finish and is white with the blue lettering: 'KASTRUP HOLMEGAARD' in a circle around the crowned swan logo. Around the outside edge of the label are the words 'BY APPOINTMENT TO H.M. THE KING OF DENMARK MADE IN DENMARK'
Kastrup glassworks, Denmark (1873-1965) merged with Holmgaard in 1965, and was known as Kastrup og Holmegaards Glasvaerker A/S, so this vase was made after the merger.

The image below shows two more vases. One a very pale ice blue with a clear stem and the other has a clear base and stem. They both have medium and small bubbles which go horizontally around the ball. They have completely flat polished bases. The round paper labels have a matt finish and are red with white lettering which states 'HOLMEGAARDS GLAS' in a circle around the crowned swan logo. The smaller label has the words 'MADE IN DENMARK' in a circle (see image below)

The following image shows a full set of the green colour. The second vase from the left has a small pontil mark in an otherwise flat base the other vases have a very smooth concave base, the same as the grey one above.(see images below). Their approximate height and stem diameters are as follows:

Height: 300mm (11 & 9/10ths inches)  Stem: 20mm (1 & 2/10ths inch)

Height: 245mm (9 & 6/10ths inches)    Stem: 26mm (1 inch 1/5th)

Height: 203mm (8 inches)                    Stem: 20mm (8/10ths inch)

Height: 159mm (6 & 2/10ths inches)    Stem: 19mm (7/10ths inch)

Below is an image of a Holmegaard catalogue of March 1959, kindly supplied by a member of the GMB (Glass Message Board) www.glassmessages.com
It shows they came in four sizes, and a candle holder. It also shows the distinctive heart shaped base and also a rounder base.

Another colour is red.

Click on the links above for other makes.