Its obviously a SOHC sandcast CB750 engine. This came out of a dump truck loaded with limestone gravel. It is unique among the odds and ends that I've found on construction sites throughout my career, most notably to date have been a knife suspected of having been used in a murder and a pair of dice.
I'm sure that for however long it was encased in limerock it is literally filled with sediment. The sick part of my brain wants to go after it with a pressure washer and see if the aluminum cases held up well enough to be salvageable, or even just to dissect it and see how full it really is. The sandcast valve cover is shattered and is missing over the #1 cylinder, the coil cover is similarly broken and partially missing so the easy to get to parts are pretty much worthless.
The dreamer in me of course wants to start a build thread and restore it. Hey @Red, do you need a spare engine for your CB? Where's @LeftLaneGuy when you need him?
It's time for Humankind to ditch the imaginary friends of our species' childhood and grow the fuck up.
"Lasse mich deine Seele dem Herrscher der Finsternis opfern"
Let me sacrifice your soul to the ruler of darkness
Always carry a bottle of whiskey when you travel in case of a snakebite. Futhermore, always carry a small snake.