Earlier models in nice condition tend toward retaining 'crisp' logo (and often nomenclature) markings decades after manufacture. As seen in one response here, many later guns tend not to have crispness from date of manufacture. Crispness may be a reasonable indicator of original finish on many models, but certainly not on the newer models. Each succeeding decade provides less ability to use such indicators of originality. Better tell-tale factors exist. Perhaps foremost is the very type and quality of finish itself. Secondary factors include uneven or substantial over-buffing. In this, over rounded frame edges, dished screw holes, etc are far better indicators. Another quite good method is of visual side by side comparison with the same model, approximate production period and same apparent style finish. Theoretically an expert refinishing could be impossible (without instruments) to differentiate from original IF the finish method is the same. Quality restoration specialists pride themselves in this matter. My take.