400 Block Identification Question

[joshhirst13]

Hey Guys. I've found pretty much all the info on Buick blocks, but this block seems a little strange. I've attached a picture to reference. My questions are as follows.
-What does the 7 stand for?
-What are the 3 dots for & the biger dot above the 7 for?
-Why is there a # missing from the date code. I'm seeing 383790, but I believe it should say 1383790 which would be for 1968-69 ??? Am I missing something here?

Thanks Everyone,
Josh

[bob k. mando]

my assumption would be that the '1' was lost in a casting flaw.

it's easy for the sand to not properly take an impression or for that impression to be blurred out and then the metal will never have a recognizable void to fill.