Is the overall 10"X10"? In the first pic it looks like a motice with a shoulder on one side and a chamfer on the other(for assemlby ease)? How wide is that mortise? Is it blind or thru? It also looks like is has another mortise about 5 inches up. What do you think fellas- Is it a post or a tie beam or a plate? to have those two mortices sitting on top of one another doesn't help. Why would you have two beams on top of one another. Depending on the type of barn it came from, they could have done any number of odd things in the design to create other rooms or stalls etc. If it is as big as the timber appears, I'm thinking it would have been a post.