It could be argued that the density of carbon steel would make it last longer than stainless, but the corrosion resistance of stainless makes it worth the trade-off. The stainless gun would last longer in a salt water environment if neither were cared for with oil, etc. (By the way, the CR prefix stands for "Corrosion Resistant"). The average shooter will never even come close to shooting enough rounds through his gun to reach the "limits" of a stainless steel gun. Your gun is likely plated, as Conley suggests. I would add that the serial number makes it such that the plating was not done by the factory. It is curious that it only says "Detonics 45" on the slide. That tends to indicate that the head gunsmith did a "massage" on the gun for its original owner, which, as Conley has suggested, may have been an employee, who later plated and sold it. The smith would always do the first one for an employee for free, but if he found out the employee sold the gun, he would do no more free work for that employee. Some of the "sleez-bag employees" realized they could get more for the gun if they could convince the buyer that the headgunsmith had slicked it up. As such, they would copy his "trade-mark", (i.e. just a simple "Detonics 45" on the slide), and lie to the potential buyer about it. If that's the case, then again, as Conley has suggested, it could be a "lunch box" gun.
...Deeton