I still dunk a batch of used stamps from my large stash into warm water now and again— to separate them from the paper they were pasted on.
The stamps are put on paper towels to dry out until they are damp, and then I press them between sheets of paper under a stack of heavy books for 24 hours.
Is that something that Tesla’s Optimus robot will ever be able to do for me— put the stamps in the water, gently rub the backs to get the glue off, dry them out, and press them under books before bringing them up to my study for me? I seriously doubt it.
* These watermarks were probably made with a so-called dandy roll. During the wet-paper phase of the paper-making process, a light roller is pressed onto the paper. The repeating pattern is embossed into the paper, compressing and thinning the fibers in that area. The thinner areas allow more light to pass through, making the watermark visible.