In your grandfather's time, anything that you want to confirm and leave a certificate for yourself must be signed and stamped. If there is no seal, you must stamp it with your right thumb.

Use red ink pad for the seal, and only dip it in red water if there is no ink pad (unofficial occasions).

The seals at that time were all made by hand. First make the printing base, smooth the engraving surface and write inverse characters on it (or write it on paper and then paste it in reverse), and then carve it with a carving knife. Those who do this are called "seal carvers, seal carvers".