Surely, not NOS.

To my eye, the stacking swivel screw does appear to be staked judging from the flattened end of the screw.

So far, the gas cylinders I have seen with the W mark on top of the rear ring have been on Oct. and Nov. '41 rifles.
In this time period, there is usually, but not always, a mark on the bottom of the tab (tang ?) of the cylinder at the rear.
As the gas cylinder does appear to be sand blasted and refinished in some way, a mark on the tab may be more difficult to see. Take a really good look at the tab and see if there is a mark there.

Don't know what effect the squiggly lines might have on performance.