It is clearly rusty metal clamp, not black plastic LNB-holder
View attachment 111121
Show us the back of the dish and all will be revealed.
But in the meantime, I agree with RimaNTSS that it's most likely a Prodelin 1.2m, possibly labelled Echostar.
The LNB holder is not very far from the original Echostar I have - and have same arms.
It's definitely not a channel master - they all have bolts in the dish face.
So based on the common types of plastic dishes of that age, and with no bolts in the dish face, Prodelin is what fits most, I think.
Which means it's a 1.2m (it'll be 135 cm tall, but the effective reflector width is 120cm).
All the Echostar branded Prodelins I have seen has a polar mount - the Prodelins usually only had an Az/El. Again, a picture from the back would tell which one it is.