The 540 model is Comet, a game that 1st came out in in June of 1985.
As for your date of manufacture, my guess is that the 4 should be a 5, which would make your's January 24th, 1985. Since it appears to be a reproduction sticker, someone maybe misread that digit.
That would make roughly 2 months of production before yours was made.
Which would equate to 24 machines built per day for a 5 day work week.
I'm totally shooting from the hip here, so I have no idea how many machines Williams made per day, or how.many days a week they operated.
Regardless of all of this, your machine looks minty! Congrats! I'm on my 3rd one. I kicked myself twice before for selling, so this one I have is a keeper. It's still my kids' fav game and they are nearly 30 years old now.
As for the serial number groupings, it looks like they skipped between 23k and 30k; why I don't know. I don't think it's a matter of incomplete data.
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