The tang safety looks like the one in patent US2465699 by Wilfred Smith and assigned to Savage Arms - applied for Dec 1946... so the date is close. (the patent is on the patents CD from the Savage Fest). The safety is shown separate from the tang and the exposed part that catches the lever is shaped the same as yours. Looking at the patent, one screw should allow the safety button to lift up so the so the stock can be removed. You might have the prototype, it logical they would have used a safety button they already had so it might be exactly the same as the shotgun's.
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Here's one by Charles Nelson for 1917, a little more complicated. (also on the CD)
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Last edited by GeneB; 08/18/19. Reason: aded another picture

Gene