Couldn't he just be a Serama with a weird tail? I've hatched a pure Silkie with sickles before, weird things happen. I don't think he can be mixed based off of where he came from. Everything about him but the shape of his sickles says Serama. Other than his tail what makes you think OEGB? What I'm seeing is a poor quality Serama. I'm still tryna get a pic of his brother. His bro is a perfect Serama, tail and all.
May I ask, where did you get him from?