Local number for me.  Called on 12/05/15.
Also called from:
360-205-7366 on 11/23/15
360-667-5263 on 12/02/15
360-268-8118 on 12/05/15
360-886-3284 on 12/05/15
All local.  All have caller ID "SSI."
I never answer and they never left a message.
BUT, a quick Google search turns up SSI as a market research company.