Last March in Castle Rock Wa. I paid $12 for a factory Western cartridge in 35 Newton. I didn't dicker, it seemed a fair price and I needed it for my collection.
I don't know that there is any such thing as a correctly headstamped 22 Newton. I could be wrong but I have never seen one that I know of and I have been collecting ammo for about 30 years.
You're right ZW I just looks it up in "Cartridges of the World" 10th edition. Printed in black and white "One of a series of cartridges developed by Charles Newton, this on did not appear in full commercial version"