Yes my opinion is they are fakes or reproduction / fantasy pieces.
Some years ago was find the Klaas combat S42 prototype, offcoarse there was not any proofs as prototype could be not proofed for approved design. The blade is nearly identical to S84/98 in grips was sidely attached tool attachment, so this was probably the real prototype before the Eickhorn of S42 design was approved.
From the german sources is avialable that was made of 500 + 1100 also of the first modell S42, which has different vertically moving locking nut differences are only in shape of WaA519
and then larger ammount of S42 with pivoted locking nut 5000-10000pcs in late 1944
no mentioning of any metall handle pieces in literature.
Since 80ies there exist some strange prototype of S42, no one was mentioned in literature since 1945 to 1980?
The scabbard is assymetrical and very rough press work,i never saw to this time E/519 on various items of Eickhorn, why would be prototypes marked E/519 and normal production WaA519?
I observed too pieces one was published on Wehrmacht Awards forum in 2012, the other probably on GDF in 2016, both had early tool serialed with digits like J.Maddox piece, has early grips and scabbard of similar design, some are cof, E/519 marked on ricasso, other E/519 on blade like here presented. For me is not believable that prototypes would have a acceptance for approved modell. Same as one piece is clearly stamped E/518 which was probably never used by Solingen. Stamping on thin blade like is on S42 outside of thicker ricasso is for me not real by german authorities! After some years they occure on internet, to proof to sale it, question is who buy it, as this are problematic pieces. The tools are marked with doubble crane Klaas logo. J.Maddox piece has 11 the other of the Waf and GDF 14 and other serialed into 20 range.
Here is E/519 on other metall handle S42, note there is no ricasso, the blade was not forged but mashined. anyway similar parts are hidden under leather buffer.
The other is E/518 piece with cof stamp here already on shaped ricasso.
So there exist metall handle S42 with E/519 on blade here by Simpsons, metall pieces unmarked (JM) , first type S42 handles with cof marking and E/518 and other with cof marking and E/519 on ricasso stamped, both the last versions had a assymetrical plastic coated metall scabbard as pictured on my first picture
Could someone believe that germans changed the proofing schema on 25 pcs of prototype bayonets more as 3 time and stamped same identical ways 5000 S42 of last contract?