what year are these commando valve covers?

Here's a theory.

They added the bump for the "new" style pcv coming in 67.

Then pulled it ahead in 66.


Now keep in mind that this is not a drastic change and can be done on the fly without affecting anything. so they can pull this ahead without obsolescence which means that they are allowed to build both versions at the same time until they run out of the old style.

Also keep in mind that they will have some engines to recycle that may have been torn down and the old valve covers recycled after the new ones have begun. There will be a period of overlap and where they will go back and forth. This change is not worth spending the manpower to make a clean break point and then incur scrap cost for the old ones. Rerun the old ones until they are all gone so they don't have to be scrapped.