What does "500 and 1" mean? In this AVWeb article, numerous references are made to 500 and 1, with other references to 3,000 and 5.

Based on the statement The current observation was 800 overcast and four miles visibility (in the second paragraph), I would presume that 500 and 1 means a 500 foot ceiling and one mile visibility, is that correct?
Yes, 500 and 1 is 500 ft ceiling and 1 mile visibility.