On ebay there’s a ‘Marken’ whistle fs. Anyone heard of it? Looks like it’s a German maker.
It looks like a Chieftain.
That whistle looks exactly like a Chieftain NR. WTF is “Marken???”
It looks like it might be a C. What is it being advertised as?
The Chieftain NR can be identified by the additional grinding of the upper surfaces around the window - this photo shows exactly that.
The Chieftain NR C whistle is pretty good - but the vendor seems either confused or someone is passing-off Phil’s work with a knock-off.
Interested to see where this goes 
Marken just means “brands”, as in brand names. So maybe the seller is confused.
I asked him . Indeed it’s a Chieftain