It really can be a bit hard to tell sometimes, when i adopted my Ash over ten years ago, he was in good condition and was neutered, i did put up notes in the neighourhood and no-one came forward , so here we are ten years later.

Ask around the neighbourhood, put out fliers if you can take a pic of him, do some ringing around the shelters etc, anyhow good luck and I hope he does have a good home or is about to get one, with you.