She looks purebred to me just in bad shape. we had a schnauzer some lady turned in today that looks exactly like the dog you found and she went into foster care. but she wasn't messy.. I hope you do find her owners, but she could have been let out looking like this and they maybe were going to get her groomed soon.. you just never know. If you don't find her owners.. are you going to keep her? I would take her to the vet if you are planning on keeping her to make sure nothing is medically wrong with her and check if she's spayed and if not if you plan on keeping her and don't find the owners, I'd spay her if she's not spayed. and it looks likes she needs to be groomed, badly.