HK MP5 Cutaway Illustration ( lemmy.world )
Sorry it's in French / Grâce à moi c'est en français. The French version I found was higher quality. Here's and English one:
https://lemmy.world/pictrs/image/c5857c86-0484-4a8c-9725-b7ee1551ca80.png
The SEF fire selector stands for Sicher = Safe, Einzelfeuer = Semiautomatic, & Feuerstoss = Automatic.
And here's an X-ray view:
https://lemmy.world/pictrs/image/f3044730-6f9c-4c13-a649-942a1ded58ce.jpeg