37E Knucklehead : Correct seat rivets ?

[Schorsch]

Own a 37E Knuckle. Try to solve some points from the last judging.
One question is: How are the correct head finish from the seat leather binding rivets.
Black or Nickl? (seat leather is black)
Georg #2781

[Paquette]

Nickle, black Japanned rivets were not used until after WW2--

[Schorsch]

cadmium rivets too?

Hi Paquette, thank you for your helpful reply. Are Nickel only used or cadmium plated
rivets too ? Georg