He looks like a Yorkie to me - purebred.
Silkies and Yorkies are difficult to tell apart often times because there are sooo many BYB'ers out there breeding Yorkies, and then they become "out of standard" and it's just so hard to tell. But even good breeders can get Yorkies off standard, so it's not always a matter of bad breeding.
A Silky was basically created from an Australian Terrier and a Yorkie, so all very closely related. Silky's have the pretty hair of a Yorkie, but more terrier-ness like an Aussie.
And often, just size doesn't mean anything. Sooo many people see large Yorkie and automatically assume it's a Silky but it's simply not the case. I've seen purebred Silky's that are 6lbs and purebred Yorkies that are 16lbs.
I often think Jackson is a Silky. But he's longer than he is tall (which is the biggest difference between them), a bit longer muzzle, bigger ears, and it's hard to explain... but even when I see other larger Yorkies, who look *nearly* identical to Jackson in person - there is just *something* different about Jackson. I don't know if it's his body, his eyes, his eyes, his snout or what (he is 16lbs, btw). But definitely personality-wise, I have yet to meet another Yorkie that acts like him in real life... he carries himself differently. So *shrugs*. I dunno. I got him from a BYB - odds that he's a Silky are probably rare, he's probably just a badly bred Yorkie. Either way, he's such an awesome dog, I don't care! And I've discovered Silky's now, and am sooo glad.