It's a giant load bearing nail -- you should hammer it back into the wall quickly before your home collapses.
Good call. Headstamp does have a "42" on it. Can't figure out the rest of the stamp though. It looks like most American-made casings have letters like "DM" on them showing where they were manufactured (Des Moines). This one has numbers. 6 9 0 and an 8 in a diamond shape. Rocketlaunch, that is definitely the shell.
If it's a .50 cal piece it would be interesting to find out where it came from. Could the 42 be the year? Do you know who owned the house previously? Were they in the military?
This bbs can never get the proper use "Your" and "you're" correct Ie: the most common mistake "your a idiot"
I think so. Most online sources say yes. My house was originally built to house a minister and his family for a nearby church. It's changed hands several times since then, but they lived here the longest. We found it in what would have been the outer garage wall originally, but is now part of our living room. It was behind some bead board-like paneling and built in bookcase in the space where insulation normally goes. I'm fortunate enough to have a neighbor that lives in the house he grew up in, I'm going to ask him about where it could have come from later today. No clue. My first thought was that maybe the builder was a WWII vet and this was his signature on the house. More likely it was just in their garage and got walled over.