Hello Leone
Those are some nice buckles, I suspect taht they are from around the time of WWI, but the ones with out script may be of a later period, the plain one in the upper left is very likely an O.R. buckle from WWI but I can not be sure.
Here is a photo of my example, it is different than any of the examples shown in your post.
I suspect that one on the lower right is a later example, as it follows the Russian pattern for buckles, and may be from a Islamic Russian Republic, but I am unsure, from what I have seen, all the WWI versions were on the German pattern.
Best wishes
Gus