Jeep flathead engine serial number?

Don't know much about flatheads. I looked at a Jeep the other day with a flathead engine in it. It says "JEEP" on the top of the head. The serial number on the water pump boss begins with a "J" and ends with an "A". I did not see a number in front of the "J".

I think that makes it a CJ-2A era engine. Correct?

 

Some info here and probably a lot more on the 2A Page
http://www.thecj2apage.com/history.html

 

Thanks duffer, that had the info I needed. According to it, the early CJ2A engines had the prefix "CJ2A" in front of the engine serial number and that number was usually found on the side of the engine. The late CJ2A engines had the prefix "J" in front of the engine serial number and that number was found on the front by the water pump.

The part that I still haven't found an answer to is the fact that the number on the engine I saw ends in an "A". I haven't seen numbers ending with a letter like that before. I'm wondering if the "A" carries some special meaning.