Holmegaard shipped out a lot of klukflasker to companies to customise for their own needs (or sometimes they did it in-house, especially before 1957 when it seems the factory's painting workshop closed) and so it could be commemorating pretty much anything within the Esso company.
Chances are, though, it will be related to shipping.
There looks to be other writing on the decanter on the other sides, or is it just a trick of refraction?