I tried to break down the horns by feature, so they're consistent across the King, New King, and Toneking models

Untitled Document
Graslitz Nauheim
1. Split bell keys 5. Left bell keys, soldered toneholes
2. Left bell keys, wire keyguards 6. Right bell keys, drawn and rolled toneholes
3. Right bell keys, wire keyguards 7. Plexiglas/"Angel Wing" keyguard
4. Right bell keys, sheet metal keyguards 8. Right bell keys, sheet metal keyguards
 

2. Left Bell Keys, Wire Keyguards
3. Right Bell Keys, Wire Keyguards
3. Right Bell Keys, Wire Keyguards
Produced from appx. s/n 89xx until approx. s/n 119xx. There is some overlap with earlier and later models.
5. Left Bell Keys, Soldered Tone Holes
7. Plexiglas Keyguards
7. Plexiglas Keyguards
... and sopranos from the same era ...
Note that most baris from this era only have the left side Plexiglas keyguard. I have seen a couple that do have the right side "angel wing," but that's uncommon.
The "Angel Wing" keyguard was patented in 1951. Based on Keilwerth's previous model, these horns were introduced after s/n 214xx. The lowest s/n I've actually seen is 219xx (1952). The highest I've seen is 50xxx (1965).