So, the squirrel hunting picture is the only intact image we have of Lee grown up. The date of it was February, either 1961 or 1962, and probably 1962.
What jumps out as a striking good match are the ears and the tubular neck. Otherwise, it's obvious that his hairline receded quite a bit and he put on weight. The Lee Harvey Oswald was never that stocky at any time in his short life.