RT8000T is the retail number and the RTT-80 is the number used by the OEM's. Same product just a different number.
This is clearly not a 1976 OEM product so do you know when the antenna was purchased/installed?
It's likely that this antenna will work just fine with Dish or DirecTV but it ABSOULUTELY will work with DirecTV now and well into the future.
What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?