In my humble opinion, this crossguard was a transitional pattern used only for a short time, probably around 1936, based on the early brass based fittings and in most cases evidence of hand chasting still being used.
It will therefore be found with both slanted and non-slant grips and as far as I am aware the blades are always early tapered.
Spitzer was another maker who utilised this crossguard for a short time amongst others but most will be marked E-Pack. I have the spitting image of Janos's second dagger with the orange grip, right down to the same characteristics of the unique hand enhancing.