What is my cool looking shelter boy?

My husband and I adopted Eddie from a shelter a few hours away from us. It was his last day on the euthanasia list due to overcrowding at the shelter so we knew we had to go get him. He’s around 75 pounds, lean muscle, he’s polydactyl on his back feet and he’s estimated at 5 years old. The shelter itself labeled him a mastiff but their facebook page said he’s a Saint Miguel Cattle Dog which is a mastiff breed. I don’t know how likely this is as that is a VERY rare breed and we got him in the Sacramento Valley area of Northern California. We’re eventually going to get a DNA test for him but it’s expensive so for now, we just wanna know what you think!