the river Lek Landsknechtdagger

[Matchlock]

It's hard to tell, the arguments vary and edged weapons are not my main expertise.

If this discussion was about a contemporary fireram, I would argue that all sources of period artwork generally tended to illustrate details of both costume and accouterments as 'characteristic' as possible, in order to ensure an optimum grade of recognition on the part of the viewer. 600-500 years ago, illuminators normally did not care for single details.
Thus, arquebuses were often depicted being fired without anyone visible to ignite them. Composite horn bows of 15th c. crossbows were illustrated in green colors - not one single existing crossbow with a green bow is known.
Animals like lions or elephants were depicted like dogs or pigs - simply because nobody cared.
It is a generally acknowleged fact in art history that detailed illustrations as well as perspective were first introduced by Early Renaissance artists like da Vinci and Dürer, both active about 1500.

Concerning the dagger grip in question, illustrated to be spirally wound in a mid-15th c. painting, I would explain this fact by pointing out the period tendency to depict all items in an 'idealized super-Gothic' decorative style - those artists cared by no means to copy an actually existing dagger. The cultural and decorative ideal was all that counted. That's why most Landsknechts in paintings of the Battle of Pavia are shown to be equipped with highly elaborate arquebuses, their stocks painted green or red, the basic Late-Gothic colors, and their Katzbalger sheaths highly decorated with colored lozenge patterns ...

In my experience, weapons - and especially firearms - actually always were the very latest objects to get decorated with characteristic stylistic features of the respective period. Thus, you will find Late-Gothic stylistic elements on firearms up to ca. 1600 - the Late-Renaisance period when they had become extinct on most other artworks, and even weapons, long ago.

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