No, it's the brass slide you are seeing, the milling marks look like wood grain. The gun is mechanically flawless, after reading your thoughts I tend to agree, it did seem repainted but it was so well done a factory rework makes sense, plus its has to have been resealed and the updated knob now fits. Thanks much for your thoughts.
Here's pic of the brass slide: (scholl to the left for more pics)
http://i168.photobucket.com/albums/u...psyqh0qkws.jpg
I wonder if the wood was factory refinished as well? It's so well done. Do you know what type of finish they used on their stocks? Looking at it and shooting it it's very hard to believe it's that old? It functions like new, very tight but I guess that's the goal at the factory. May have replaced old warn parts.