I dont think the 8 panel horns are particularly hard to come by. They were an upgrade from the 10" cone, and it seems that about half of the A, B & C Gems that turn up have them. They were then standard issue with the maroon Model D. The same horn was also supplied with the Fireside model.
Yours appears to be original to the machine, as later horns screwed together/apart, separating the cone & flare.
The larger horn delivers better sound quality than the tiny 10" cone horn, which makes it more desirable amongst collectors, but I'm not sure what the difference in price is between the two. I wouldn't expect it to be very much??
It should have a one piece crane that sits in the hole in the casting, at the front of the mandrel gears.
Probably the best way to determine value would be to keep an eye on ebay & see what the same machine with 8 panel horn are fetching these days.
Matt Brown has a Model B on his website that he sold on Ebay a couple years ago for $850, but it was in exceptional condition & included the 10" & 8 panel horns.
Of course the market isn't what it used to be either, so I think you could probably halve that price these days.
I dont suppose you could tell me the dimensions of the wooden base

I bought a beat up Model B a week or so ago, which was minus the lid & base. I'd like to make a new base of the right size for now, until a base & lid turn up on Ebay.
I actually made a base yesterday & finished it last night, but I dont mind making another of the correct size
