Whistle collectors are different don't you think ?? We don't spend as much time looking through windows as we do looking at them !!!!
It's all about the shape, level and effect………
For example how high up is the window on your whistle ??
How much does the angle affect the sound ?? — The diaphragm or wedge in relationship to it.
How large is the opening ??
What shape is it ??
Does the manufacturer vary it or modify it on the same whistle model or is there progression perhaps ?? Helping to date it ??
Is it round, oval, straight sided or curved ??
Are there two windows and do they each have different characteristics that can be seen the same on each whistle from that maker ?? Helping to identify the manufacturing process that particular maker used ??
Gives new meaning to window shopping…..