"Built in batches" is similar to the Triumph situation.

The four, five, six or seven NUMBERS in the serial number of each bike DO NOT indicate the actual number of THAT "model" produced in any given year,
If you know the serial number of the FIRST "A65" of any model that was produced in that model year can you determine (or "guess) when your bike rolled down the assembly line.

The serial number determines WHEN in the sequence that engine was built. The model designation, such as "A65T" or A65L" informs you what is INSIDE that engine, such as it's compression ratio, and / or cams.

My study of Triumph serial numbers often shows when batches of some models were destined for the USA. An example is the large group of Triumph "Cubs" which appeared in the USA in mid-1961. About a dozen of close-sequenced serial numbers indicates to me that those were of one batch built for the U.S market.