I am looking at a beautiful 1970 Black Z28 to purchase. I know that the color black was not available this year. The owner tells me that it apparently was a special order as the original trim tag only notes the interior designation and nothing for the paint color. Did this ever happen and if so how rare is this?

It would need to have -- for the PNT code.

My friend has a 73 -- car that was originally black, which wasnt available in 73 either.

if a dealer ordered the car special paint it would not have a paint code. you need to look for a build sheet. my 70 LS6 chevelle is a special paint color with no stamping on the cowl tag. been in family since new. it has trim stamp 771 but nothing on paint code. yes it is very possible and likley but what was the special color. mine was ordered code 53 camaro gold. i have the copys of the newspaper adds from the week starting june 1970. you can see them on the team chevelle site. look for nugget gold and bigblock70 post's:beers:

It could also have a -- paint code if it was an original color with stripes deleted. Some people take advantage of that to paint a car a desirable color. If you are in to correctness you may have to trace the car back to an early owner to prove it. If a car is frame off restored there may be no original paint left anywhere to find. But most people take pics during the resto so ask to see them.