Here's a good page about APM, with a brief (but interesting) history:
http://www.themusicden.com/m-2660-americanplating.aspx
Looking at the catalog designations, it's pretty clear that the 1. the number is arbitrary; 2. N = nickel color (as G = gold color, LQ = lacquered, etc.); and 3. C = the key of the instrument.
This is one of those funky little companies like Trophy and Herco and Generation that have been around for a long time as sources for the odd little items. When I was a buyer for Sam Ash they were handled mostly by jobbers (wholesale consolidators). Need a gross of ligature screws or bassoon staples? They've got 'em.
My guess with items like this fife or the Song Flute is that they were probably created at the request of a particular customer at some point in the distant past, then kept in the catalog because they fill an odd niche. And as with Gen whistles, the details may be long lost in the mists of time.
As I recall of the Song Whistles (which I used to sell), the quality control is spotty at best. Some were good, some not. The manufacturing process may be unchanged for 100 years, and not really up to consistent embouchure/fipple tolerances. But they are what they are.
Vivat diabolus in musica! MTGuru's (old)
GG Clips /
Blackbird Clips
Joel Barish: Is there any risk of brain damage?
Dr. Mierzwiak: Well, technically speaking, the procedure
is brain damage.