My wife and I visited the Historical museum while in Oslo for a four-day side-trip from Stockholm. We paid a total of 200 NOK. We arrived at about noon on a rainy Sunday. We probably went in with a bit of a sour attitude, as it was our fifth museum in a bit more than a week, and we had been hoping today would be a sunny, warmer day for more outdoorsy things.
All that said, we were pleasantly surprised by the exhibits. Unlike all the other museums we visited, the Historical was a bit all over the place with its displays. Our self-guided tour started slowly as we weren’t captivated by the displays on the first floor. But the Egyptology exhibit was very good (arguably it is somewhat limited, but there are twice as many mummies on display at the Historical as there are at the Louvre in Paris). We also enjoyed the display relating to gold and gold coins. We lingered for some time in the Viking-era exhibit, and also enjoyed the Samurai display, even though it seemed less connected to any of the other exhibits.
We did find that the security staff in some of the halls seemed to take their job a bit too seriously. At one point, an attendant jumped on a visitor for taking pictures of the gold medal display. For the next half hour, we were reluctant to take photos unless we saw other visitors taking pictures, because we were confused about what we were permitted to photograph and what we weren’t (there was no signage). In general, some of those staff seemed to be lurking, trying to catch someone in the act of something they weren’t actually doing. Later, we thought maybe the issue with the photography was that the person had used a flash with their photo. Again, there was no signage.
In total, we stayed about an hour and a half, and the weather had improved a bit by the time we left.