3,7 cm Pak or Flak ? - Germans 37mm

[37bis]

I have several 3.7cm I having trouble identifying specifically, lack sufficient documentation.
For example those whose photos are attached.
What is the name of these models? Is this Pak or Flak (or both)?
Thanks

1. Practice ? Übung ?
2. Practice ? Übung ?
3. Practice Übung

 

[Weasel]

The first two bare metal ones are Flak and the last is for the Pak as far as i am aware, and yes practice all three of them.
Best regards Weasel.

 

[blackwatch]

2. 3,7 cm H-Pzgr. Üb, (3,7 cm BK)
3. 3,7 cm Sprgr 18 BL (3,7 cm Pak)

 

[Weasel]

Thank you Blackwatch i forgot to mention the first two were for the BK
Best regards Weasel.