There are "manufacturers", there are "planners", and there are "dreamers".
You also have primary and boutique, and there is only ONE primary, Stern.
JJP is not a primary, as they have produced only two machines in nearly 6 years.
Spooky has done nearly the same amount.
To qualify as a manufacturer, the company has to have actually BUILT a game (or kit) and shipped it to customers in the past 5+ years and still are active in the industry:
If you use this category definition:
1 ) Stern (Multiple titles)
2 ) JJP (WoZ, TH, DI (has NOT shipped))
3 ) Spooky (AMH, RZ, Dominoes, Jetsons (has NOT shipped))
4 ) Dutch Pinball (BoP 2.0, TBL)
5 ) Heighway (FT, Alien)
6 ) American Pinball (MG, just squeaked by here)
7 ) PPS/CGC (MMr, AFMr (planned))
8 ) Quetzal Pinball (CNemo)
9 ) Riot Pinball (TWoO)
If you include all "planners" you need:
10 ) P3 (Multi Morphic)
11 ) Silver Castle Pinball (PPTS)
12 ) Homepin (Thunderbirds)
If you include all "dreamers" including homebrews you need:
A complete laundry list of madness with detergent still needing to be added.