That looks like what a master carpenter friend of mine called a scarf(sp?) joint. Traditional splice when lumber is not available in the length needed. I know there were limitations on where and when he would use them, but I can't recall those details. Full length lumber is preferred, but sometimes you just can't get a 60' 2"x8" or what ever.

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Jim Luttrall
Mr. Inspector.net, Inc.
Allen, Texas 75002