I am at work now and don't have access to the gas cylinder now, but I will check for a divit or dished area to the rear of the stacking swivel screw this evening.

Thanks to you and Bill Ricca for the article. The finish on this one is great so it held up well if it is the original finish.

Looks like I probably have a nice gas cylinder to go on one of my WWII SA. Garands.