Hey everyone. I am now the owner of this badge and the others I posted two weeks ago. While inspecting it, I saw it had engraving on the back. Was wondering if anyone knew anything about it. It’s SS which scares me, but looks to have been there a while. It reads as follows, (something I cant see) Heinrich Mathias 3? SS flak?- Abt. Das Reich Fpi Nr. 39858

Anything would be amazing. Would love to find out who he was. Also, does anyone know what the Fpi. Nr. is for?
Thanks in advance,
C.S

- - Updated - -

Note: The nine is done like the period nine, meaning looking like a g. Thanks agian!