Above is a clip from Tibor's last letter, it is, in fact, the first page to the bottom right of that page.
you should be able to relatively clearly make out micro written numbers with some letters within the marked/elliptical areas; they are darker grey against a light grey background, you will need to let your eyes rest and become accustomed to the shade differences.
To the top right of this image is another clip overlayed and outlined in a rectangular red box. It is from another instance of microcode and you will see that the arrow is pointing at a small letter 'x'. Not in particular the style of that 'x', t is stylised to the extent that the lower part of the two strokes are slightly curved. Now compare that 'x' to the one on Tibor's letter, it also has a small arrow pointing to it. they are very similar in shape enough to suggest that they could have been written by the same person.
For the record, the micro-writing in the rectangle was lifted from the code page from a location just beneath and between the first letter S and A on the last line.
The good news is that Tibor's letter is still in existence and we have access to it for further examination. We'll update you as soon as we have any fresh information.