Fighting/trench-knives or so called Grabendolche have about the same size as the later HJ knives - Fahrtenmesser
Its easy to see that the WW1 birdshead knives by WKC could be one of knives that they looked at desiging the later HJ knife.

In this case it also goes a bit futher, as in the very late build of WKC Knives 1941-42 (mostly unmarked ones) the same narrow bowie blade appears.
It looks like they used an old ww1 stock of old blades to build their last lot of HJ knives.
I have added 2 pictures of Victormann collection which showes them from WW1 to 1942 ( thank Herrmann :)) got the pics when i bought a WKC HJ Knife with bowieblade from him.

The WW1 Hammesfahr trenchknife bears the bufferpad but other than that its a solid knife, the WKC birdshead knife is a hard to find one and its blade is still in great condition, the scabbard did a terrific job, considering it has no bufferpad to loch the scabbards troath!
Nice detail is the logo, which have been stamped twice.

The Grawiso Mottoed early transitional has an early scabbard with only the front runnerits has the Stocko marked button.
The blade is in lovely condition with a clear Motto and stillhaving crossgrain present, on the other side the makers logo on the blade and RZM code on the ricasso.

Enjoy the pics.
Regards,
Ger

Click to enlarge the picture