I'll tell a story now. The last Gleason I found for a client was stapled, in 1945, inside a playbill. The signature was Gleason's, in pencil, and the brown kraft type paper had left reverse acidic stains on the opposing pages as well as corresponding rust marks from the staples. I don't think there was much "opinion" in play here. This is why I like so many different qualities and features of an autograph, such as dedications and inscriptions. But it could have all of this - it must be Gleason's hand. I don't think it has to be opinions, there are many other textures to feel to help reach a conclusion of authorship.