1915 Hungary 10 Fillér - IV. Károly - Iron

N#10041

In the picture displayed here, there is some kind of mintmark under K.B, a 4 petal rosette of sorts. Is that usual for this coin ?

Also, if there are iron versions without this mark, is there a visual difference between this coin and the nickel version? 

N#7098

Thx.

Mint marks identify mints. The K·B is the mint mark, the rosette you mention isn't a mint mark.

I believe the rosette is a design change to identify the metal change and any exceptions (errors) would be valuable.