A thought to the "57" versions...
WW1 cannot of course be a 57 version, but it could be post WW2.
About 10 years ago i called S&L to ask about a 57 RK.
They said they had none, and i should contact Werner Sauer of the BDOS, he would note my order and I assume with enough orders, they would whip up a batch....
I suppose any legit Veterans who wanted a 57 RK already had them, and now it was only for collectors....
Technically it means (I suppose) that for years S&L has been making RKs for the collectors market, and not for recipients...