Kriegsmarine WKC Crossguard year of introduction question

[Tomaz]

Hello guys,
Shown below is the crossguard that is usually seen on WKC M38s, does anyone know the date this guard was introduced? I have seen it on a few daggers fit with the "replacement" pommel which indicates M29 production, but most WKC M29s i have seen have their earlier guard with the drilled release button. Could this guard have been introduced just prior to the introduction of the M38 so can be found on legitimate M29s, or should it just be seen on their M38s ?

Thanks
Tomaz.