A 5D serial number dates from 1979. When all of the "D" numbers were used, they began adding a letter in front of the "D". They went all the way up to 30D... before the new three letter system was implemented.
An ACS..... date is likely from 1983, but could be up to 1986. This specific code isn't listed in the book but others very close are shown.
Hope this helps.
Steve