Help identifying dog breed

A week ago, a small business owner abandoned this dog, simply tied it to a fence and left. The dog is in an OK shape, good weight, healthy but it shows indications of abuse, plus its not properly trained, since from the little information I have gathered the former owner kept it locked in for 3 years in an outdoor 10 feet by 10 feet yard.

I am not an expert in dog breeds, and I understand this might be a mixed breed. I am just trying to gather as much information about her as I can in order to train her better and find a good match for her re-homing process.

I have seen dogs like these before, but I can't find any pictures of them online. So far she seems to have a gentle disposition, quiet, and playful. But I don't want to make assumptions.

Any indication will be appreciated.