WW2 German luftwaffe ground combat badge

This is the German Luftwaffe ground combat badge for three assaults by Luftwaffe ground troops.
Badge is worn on the combat jacket on the left breast pocket.
The badge is of the solid version.
It is marked on the back in the metal with “G.B.”, but I don’t know what it stands for.
Looks good to me but don’t know for 100% if it is original.
For this reason I tried to keep the price reasonable.

Marked on the back with “G.B.”
Used / complete condition.