When it was signed is irrelevant. The signature that was signed is limited to the name Ray or Roy. The Moore is in different colored ink. All that is known from it is that Ray or Roy signed the yearbook. Which Roy or Ray is a matter of conjecture. These two names are not terribly rare. A handwriting expert would tell if the mismatched styles of the Roy and the Moore could constitute an actual signature but the ladies- Nelson and Allred, are unwilling to hazard such inspection.
Actually, handwriting expert Arthur Anthony concluded that it was Roy Moore’s signature. And that fact that the entry was relatively long (it was not just his signature) would help make the analysis even more sure.