Firstly i would measure the width of blade on crossguard, as mentioned its a narrow pattern with 24mm or a normal blade with 25mm.
Secondly as mentioned before this is a war period replacement, personally i would tend to Eickhorn production from mashining of blade. The scabbard from the last picture looks like have only one inner spring, question remains the mouth piece with colar and other part of spring is missing here or was made so, should be probably inspected on real. The screw is really low position over hook, the hook looks unlined, which could be a simplifyed variation of war period.
The real production period is 1942 and later.
I compared the RBD marking and it looks identical to earlier pieces, difference is in size of digits, which are smaller here 138 as on other RBD KS pieces, which means it was done much later as the first delivery from 30ies. RBD modells used a KS98 scabbard type with thick mouthpiece not the S84/98 scabbards as pictured here in comparation. Should be compared with other wartime RBD Kassel piece.