Ok, I went back over my notes and yes, from the factory, all three year Camaro Coupes used the rectangular grille like the one on John's car. However, there's a possibility that the one in the Craigslist ad "might" be a dealer installed accessory. These were designed to be used on multiple models (in 1969, the dealer installed C50 Rear Defogger - P/N 993514 - was also used on the 1969 Nova).
It "might" also be a Pontiac piece, or even a Buick or Olds grille, I just don't have enough info to know for sure.
However, the motor date of 10-68 definitely indicates it's for a 1969 model year car.
Ed