I have never heard of a MEP0002a, going to the Government Liquidation (you said liquidators, did you mean liquidation?) web site I find 106 MEP-002a generators auctions listed at the moment, some in your state. As to the manufacturers name, they are all the same, it was just a matter of who had the assembly contract, they used the exact same parts, plus by now the vast majority have been through the rebuild process enough times that you are likely to get a mix and match set anyway, not that there is an easy way to tell. Again year they were "built" means very little and will range from about 1970-1990, since parts over the years were virtually identical (I think there were 3 different starters used, and a few styles of drop in replacement injectors, but otherwise things are nearly identical) , and newer parts would likely be installed if needed at when the generator was serviced or rebuilt.
You mention that you want to buy from GL, but I thought I should mention to you that we have a member here that sells running used MEP-002a's in your state, which may be worth it instead of playing the GL dice roll. In my experience (having bought 5 generators from GL now), sometimes you get one that runs with very little or no work, and sometimes you buy one with a seized engine, and sometimes it is somewhere in between.
Ike