Don't forget the poly choke....
My first gun was a 20 ga Mossberg 500 with a poly-choke and no SN. Ugly, but I didn't know any better, growing up surrounded by repeaters. It went in the safe after I got back into shooting and discovered that guns can be had with two barrels. I pulled it out recently, dropped in a snap cap and when I tried to pull the trigger, I thought the safety was on - it wasn't. It took less effort to cycle shells through that gun than to drop the hammer. I sold it but I kinda miss it . . . .
Dad has a M12 20 ga. that I hope not to get for a long time, but when I do, that will be a fun gun to shoot.
I don't care for autos but there is something about a pump gun with a lot of field wear - an American icon, like GLS says.