3 Pfenninge Prussia KM 453

Hello friends, in the SCWC from Krause they divide the 3 Pfenninge Prussia KM 453 in 2 coins, KM453 and KM453a...Can anyone explain me the real difference? In Numista is only one entry for KM 453... Unfortunately I don't have the Schon Catalog of German Coins...Thanks all!!
https://en.numista.com/catalogue/pieces6170.html

Here is an excerpt of the German coins catalog from KM

And here is an excerpt of German AKS-catalogue (however: only one number: #90):



Interesting: In German Kahnt-catalogue no differences are described (only one number: #51).

Thanks Leitwolf and Idolenz... I have 3 in my collection and really the coins post 1857 are thinner than the early ones...I think Krause put this difference between the "types"... Interesting that in the German Catalog has no difference, which number catalog could be that on the Note? REF 35 and REF 49?