I always learn about the coinmaking process from your posts. Thank you!
Before posting my earlier comment, I looked over the 10 examples of this coin on CoinArchives. Going from top to bottom of the coin, here are the differences I see (listing my observations on the other 10 examples first, then the OP coin)
1. hairline meets forehead below the I in KAISER, not the A
2. horizontal wrinkles in forehead, even in worn examples
3. no deep furrow in hairlines left of ear; no deep notch at back of hair at same level as top of ear
4. no deep groove in rim of right nostril
5. 7 beads between G in KONIG AND P in PREUSSEN, not 5-6
6. sideburns are never below ear
7. 13 beads between N in PREUSSEN and W in WILHELM, not 10
There were proofs minted of this coin. ANother thought I had is that the proof dies were different (but this doesn't square with my hunches about the sensibilities of a Prussian engraver

)
Edited by tdziemia
02/03/2019 6:10 pm