First - welcome to the site. Hope you find the information shared and the support helpful in your efforts
I have a 69 S-code built June 3 of 1969. Four-speed factory AC car Mach1. Mine has the original engine never been removed from the vehicle. It has the painted valve covers an air cleaner. There was no chrome dress up option for these vehicles. By my understanding, because the engine was being phased out, the late production ones used the painted versions. Probably because the chrome parts supply ran out before the end of the model year. This was verbally shared with me. But I have not been able to find documentation to prove this otherwise.
Thanks
During the year you had the option though the percentage of how many owners choose to pay a little more or the chrome is unknown to me
Need to look at the MPC for 70 to see if they still carried the chrome valve covers - if so that would suggest that the story told you was something made up by someone but no way of telling without more effort
Looking at what I have I thought I would offer the following for reference purposes. Holes in certain parts of the year only means that I've not collected enough data from those periods. Since this was an engine plant thing where the car was build does not make a difference or should not - though in a really odd, odd situation I guess a delivery problem with air cleaners would change some details but we have no indication that took place. Just trying to cover all bases
Added approx month just for comparison purposes
Standard warnings about collecting and comparing but we have to start with something and the greater the numbers the more chance that the altered cars will stand out in surveys
Unrestored cars of course
9F103xxx - chrome - Sept 68
9F108xxx - painted - Sept 68
9T123xxx - painted - Oct 68
9R120xxx - chrome - Nov 68
9T1515xx - chrome - Dec 68
9F138xxx - chrome - Dec 68
9F139xxx - chrome - Dec 68
9T1565xx - chrome - Dec 68
9R1349xx - painted - Jan 69
9R1389xx - painted - Feb 69
9R1429xx - chrome - Feb 69
9T1757xx - painted - Feb 69
9R1561xx - chrome - Mar 69
9R1572xx - painted - Mar 69
9T189xxx - chrome - April 69
9F1857xx - painted - April 69
9F1978xx - painted - May 69
9T201xxx - painted - May 69