At the end of this letter/communication, the authentic zodiac had signed off the text with his usual crosshairs logo only with what appeared as a clock numbers’ places on it, with an X placed on top of a few of the numbers. It’s really is a weird/twisted logic counter-clockwise list of the murders he committed/claimed to have committed.

At this is the confirmation that zodiac didn’t killed Robert Domingos and Linda Edwards as the 2 of them were killed in June 4th, of 1963.

As you can see here: https://imgur.com/gallery/y7xiliL

And here is most likely how the zodiac looked at his watch upon signing the "bus bomb" letter: https://imgur.com/gallery/fDIXJwa