Since we're visited this thread again thought I would post a handful of pictures of some additional details and findings.
As been discussed above the question about dating the battery thought I would stay with that and a detail about the posts found on 66-67 Autolite battiers I have pictures of. Some of these pictures have been posted on forums, sent to me or ones I've taken
So far we've seen a date on the bottom that possibly identifies when the base of the case was cast/made.
Then we have another date visible from above that may identify when the battery was assembled - on the negative post base or it may be related to the starting date for the warranty. On batteries from 67 I've got a couple of cases where there is a heat stamp on the top which I do believe is warranty related
In addition to the two pictures above that show dates and post design being used in spring of 66 I offer the following.
Two other post designs in addition to the one above. One with a raised section of the case, a ring and another that is scalloped. The scalloped version has a June 67 date it appears. Don't know what the information or coding is on the end of the negative post.
What I believe is a 1967 date example with casting date and the top heat stamp date and additional coding
Another example of the same heat stamped top surface. Same location. This pictures is one from Bob G but can't make out for certain the second digit of the year 6?
Hope this helps the discussion, understanding and others