I am considering buying a S&W Model 27-2 8 3/8" barrel. The seller has two, a 6" and the 8 3/8" that I am considering. Both look like new in box (wood presentation box). Similar to what is listed in the Standard Catalog of S&W both have "-1975 Target trigger, target hammer Patridge front sight, introduced with Goncalo Alves stocks and case". Both include all the tools and paperwork. However, neither guns stocks have the guns serial number stamped on them. Everything makes these guns look like "New In Box" but there are no serial numbers stamped on the inside of the stocks. Is this unusual?