I think this possibility of info on the door is very interesting. I’m currently kind of buying that there is some writing hidden in that one photo, with an M and L visible.

It is interesting to look for other photos and find what looks like an image of the car at night surrounded by police with no writing in that part of the door.

I think it would be great if someone could post the best photos of the door that we have – in chronological order of their release to the public and citing where they are sourced from.

I just keep staring at that sheet of paper and thinking, "Why would it be taped on there if not to cover something up?"
I just can’t think of a good reason…

Also – and this is totally speculative… but what if Z used an "invisible ink" that revealed the extra writing after being dusted for prints?

Could it just be an evidence number?

"Fisherman’sFriend wrote"

It is interesting to look for other photos and find what looks like an image of the car at night surrounded by police with no writing in that part of the door.

The first photo below looks to have been taken on the night at LB. It looks a little overexposed, but that could just be the lighting used on the door, or maybe someone has adjusted the photo before posting.

Regardless, you can see the same markings in this photo and the one below it. For example, at the right hand end of the door knob, and in the area to the right of the Zodiac symbol. No sign of any additional writing or markings in either of the two areas later covered by the cardboard squares.

I just keep staring at that sheet of paper and thinking, "Why would it be taped on there if not to cover something up?"
I just can’t think of a good reason…

If you’re referring to the main sheer of paper, then, yes, it was taped on there to cover something up – firstly, the full Zodiac message, and then "By Knife". The two squares of cardboard don’t appear to be taped to anything, they look to have been propped up in their respective positions. Also, only the right hand piece of cardboard looks to have been placed there specifically to cover that area of the door. The right hand piece is fairly low down, almost flat by comparison, and is not really covering much of the door.