Below is the link. This was on display in the Golden Lane, in Prague Castle. I apologize for the poor quality. There is one example of the kind of "description" attached to this album. But every example had one, and make no mistake, these were presented as actual historical artifacts, hundreds of years old.
There are things like a viking helmet with horns, varieties of flails, axes/swords/polearms with guns attached, and other things.
The horned viking helmet is indeed a reason to be suspicious, as that's a well known misconception.
The helmets do look very strange to me. They seem hardly to have been affected by the 1000 years or more that have passed since they were made. Nevertheless they seem to be extremely plain, without any kind of decoration or engraving. Such plain helmets would at some point have been either melted down or, less likely, have been thrown away or lost, but then they should be damaged/rusty.
So I think your suspicion is correct, these items are fakes. I can't even call them reproductions, because in some cases there are no items they could be reproductions of.
Which museum were you in? It's about 15 years since I was there, but I remember Golden Lane as a more commercial area really. So I suspect it was maybe a museum in the same way all these "torture museums" are museums?