Thanks Scorpion8r.
... Back '64, Dad gave me a 20ga pump shotgun when I got my first hunting license, several decades ago -- got my first pheasant with it. As my boys grew up each of them in turn used that shotgun for hunting, target, clay. That shotgun always worked very well for us. And each boy added something to the gun: Sling swivels, recoil pad, carry case, ...
But as with many folks, Life happened, the boys grew up, moved out, and each opted for 12g, so the ol' 20ga was stored in a place of safety. A short while ago I picked up my new 870, and remembered the old 20ga in the back of the security cabinet, so I brought it out:
Remington 870 Wingmaster, 20 Ga. (Whaddaya know -- Dad did like me after all

)
Since then I have been looking into what information the serial # could provide, just 6 numbers followed by 'X': nnnnnnX. I'm fairly certain Dad picked it up used, so its manufacture date is early '60's.
Think I will look into some of the other threads.