after a little "internet research" I came up with a few interesting facts.
1. Mylar sticker = Motor Vehicle Certification Label (official name)
2. content of certification = name of manufacturer, date of the applicable U.S. FEDERAL MOTOR VEHICLE SAFETY STANARDS IN EFFECT ON THE DATE OF MANFACTURE SHOWN ABOVE.
3. The Label must be attached in a way that it may not altered or remover with out destroying it.
4. The Label must be made in contrasting color with block letters black in color and 3/32's tall
5. label to be attached on door near latch assembly (other locations provided also ,shortened for post).
there are more requirements but for the sake of necessity of the point I'm about to make I'll stop here.

the point I am going to make is not speculation, but more towards "documentation". meaning I obtained my information from a U.S. Government website, and am awaiting a printed copy of a Government Document. Certification Standards 49 cfr part 567.6 (1). the trickey part is finding the ordinal bill that was introduced in 1969 for the 1970 model year and that is the copy I am waiting to receive. as soon as i received I will post for all to see .
The point being that the manufacture had complete control of how they certified they were in compliance of FEDERAL MOTOR VECHILE SAFETY STANARDS. What Chrysler did was certify that the vehicle in question was "compliant" to the FEDERAL MOTOR VECHILE SAFETY STANDARDS in effect on that particular date. That is not necessarily the date it was manufactured ,but the date of safety standards that were in in effect at the manufacturing. the manufacture's were given several compliance statements to chose from and it was up to their discretion to chose which best fit their product. There was also no certain time period that the MOTOR VECHILE CERTIFICATION LABEL was printed or placed on the vechile other than before it left the manufacturing plant. The "Standards " amended quite a few times since then , But 1970 model year was the first for the certification label ,with the exception of the 1969 mid year Daytona which should be self explanatory. all in all I think that the certification sticker is not the actual date of manufacturing, but instead noting that the vehicle was built under those standards in effect on that date range. note that if it was ment to be the production date it probably had a day date listed. It was required to certify compliance with federal safety stanards.