Russian AKM 6X4 Scabbard Tension Spring Variations

[Mr. B.]

Recently I found this illustration page in a Russian reference. It shows the four different tension springs used in Russian AKM 6X4 bayonet scabbards. Just out of curiosity, I inspected the 39 Russian 6X4 scabbards I currently have. I hoped to find a correlation between early vs late issue or Tula vs Izhevsk usages.
Here is what I found. All of my Izhevsk 6X4 scabbards with matching early Type I to late Type III bayonets had the Type 15 springs, (top left, front and back). All of my Tula 6X4 scabbards with matching early Type I to late Type II bayonets had the Type 16 springs, (top right, front and back). I did not find any of the Type 17 or Type 18 springs, (bottom row). They are basically the same, just reversed images probably to simplify manufacture. I wonder where and when they were used?
Below are the illustrations, also front and back pictures of the spring in my collection. Mike

[Brian]

Another great find and post. Thanks Mike!