I'm struggling to understand
手に実際穿った part in the following passage.
What meaning does it have?
I tried to make a fast translation of the the sentences with the part I cannot grasp, except the part itself.
Letters first became visible when I looked through magnifying glass. Becoming faintly visible, they are scratched here and there which makes them impossible to read in such places. Judging by letters shape it makes the feeling as if 手に実際穿った.
Context: The speaker receives a strange letter, with empty contents. When he tried to look for the fingerprints he seen the print of the whole hand on a letter paper. Now he tried to look through magnifying glass.
I think now, after remembering all of the context, I more or less understood it. So to the speaker those small letters felt like the writer of the letter drilled them in his hand and then made the hand print on a paper.