Chicken or duck egg?

[Y master]

I have been incubating this egg (along with a couple other different breeds of chicken) and assumed it was a chicken egg, it's from my chickens, but I have chickens and Peking duck together which use the same nesting spaces and was starting to wonder the possibility of it being a duck egg? I don't mind if it is because I'm incubating a dozen Saxony bantam ducks anyways. So my question is can anyone tell if this is just a large chicken egg or Peking duck egg?
Thanks (also if it's a chicken egg it hatches in 7 days or a duck egg 14)

 

[oldhenlikesdogs]

Looks chicken to me.

 

[aart]

I know next to nothing about incubating duck eggs but....
Would you be able to tell from stage of development when candling?