As stated, Proto is Dye's sister company, along with several others such as Dye Snow and Dye CNC to name a couple.
Proto is centred around the budget end of the paintball market from producing some of the better basic rental masks out there, right up to the tournament scene, where most the dye line up will have a budget equivalent in the Proto range.
There is more of a gap between the two lines theses days than a few years ago, when the PM was more or less a DM without self cleaning eyes. However I'd still happily rock any of the top end Proto kit.
I thought all the parts are made in china or some such with the dye's being assembled in the states and the proto's assembled at source, or I might be about 5 years out of date with this information, or I might have made it all up in my confused mindbrain.