Ruger's early production models had the red eagle logo (left side only) and a steel front sight. But there were pre-production models with no logo and even with plain wood grips. A brass sight blade is a fairly common pre-production item for fixed sight guns so the sight can be filed easily to determine the right height for the produciton gun.
So is the seller full of it? Maybe, maybe not. I would like to see pictures if possible.