For model year(s) 69 and 70 (and through at least 73), the original factory supplied extensions were supplied by Schrader and delivered in a brown paper container that, most likely, was deep sixed during new car prep. The reproductions have the white rounded center and were reproduced (probably) from the later 'in service' units pictured above.
I have only seen two sets (four to a set) of original Schrader extensions for sale. They are certainly a tough score today. Good luck with your search.
Regards,
Mark
