Build date Question 1970

[SSRSZL3]

A little Back Ground first 1970 SSRS 375hp Camaro 1 of 600 production run Original engine was not in car .I have both the Build sheets but the place were the date built ect ect has those brown spring markes all I can read with a Magnifier is looks like 16 has anyone tried to clean up that brown marks with some type of ?? The reason I want this info is wanting to get as close to the orignial date for like the heads and other parts .I have a correct coded 1970 Block should I match it to the block with heads ect ect or look somewere on car for date .Thanks Ron