My pleasure KD,
Exactly right this mask and filter were both made by ADG Auergesellschaft of Berlin . The KuK marking shows it was made specifically for Austrian use.
If you look closely, you will notice the thickness of the straps and also the addition of "Spiralbaender" which was the new harness system featuring cloth covered springs. Both of these features identify this mask as the second model of what you're calling the gummi mask.
The canister is indeed the A3 variant which was only made by the Austrians. I would definitely consider it a fully authentic gummi kit [mask, filter, and canister]. It's a very rare example showing a combination of German and Austrian made parts making a complete set that would have been issued to the Austrian army during WWI.
All the best John Josef