It's perplexing because it feels like it was a targetted strike, not random kids being hooligans. I did a little walk around the neighborhood and I didn't see any other egged houses; if it was random kids I would have expected to see a whole dozen eggs used up in a spree down the street.
Also my house has a big fence in front of it with a gate you have to open. There's no way you could hit the front door over the fence, somebody specifically opened the gate and came in and threw the egg. That's not the kind of thing random kids on a spree do, they go for the easiest targets.
So now I'm trying to puzzle out who has a grudge against me that would do this (and knows my address). All I can think of is Old Lady Who Ran Into Me. Maybe that's how you settled scores back in the 50's.
The funny thing is this is exactly the kind of thing I often think about doing to people who have wronged me (like landlords, neighbors, and so on). I wish the person had left a note.