The plaster in the following images is from 1958.
What is the likelihood of it containing asbestos?
if its from the 50's the chances are very high. however, it is region specific often. if you are located in the eastern us or canada, there is a very good chance of it. if you are worried about it, you can remove a small sample and take it to a local health lab or college chemistry lab and have it tested.
After a lab-test, I can confirm that the plaster does not contain asbestos. I have been told by craftsmen that the probability of plaster containing asbestos in Denmark is almost non-existing.