New England horns usually have a flat plug made of soft wood, usually pine, with relatively wide annular rings in wood compared to hard wood plugs. While not all New England horns have faceted spout tips [and at times a faceted spout throat below the tip], if you want to make sure [well, as sure as you can] it's a N.E. horn, get one with at least a faceted spout tip. Like most horns, as they got late into the percussion era, even some of the N.E. details began to fade away, with horns becoming very generic looking... but N.E. horns usually retained their soft wood plugs to the very end.
Shelby Gallien