Short off topic R-390 question

[Joe]

A fellow 150 miles away has 2 R-390's (non A's) one is a Collins the other cleaner but no nameplate (Motorola? )
Does anyone know if there are any contractor built one's to stay away from
Unlike the cheaper "A' models I thought only Collins made the nice sounding R-390 with the RC filter's, 
I want to jump on this but didn't have enough time to research it.
They both are in a rack and he is willing to look inside the (no name plate one) if I can tell him what to look for before driving to get it.
Regards, Joe

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