I have a couple of those too.
I think they're Post War Norwegian.
You might be right. The leather is for sure post war. I have the feeling that they just used left over wartime metal hardware.
Although, the one sling does appear to have a faded stamp consistent with Wehrmacht issued slings shown on Bergflak which I find strange. The obviously later added crossed sword stamp is still bring and clear. You can kind of see it on the top sling, middle picture to the left of the "50"