Oh! my mistake. I was looking at my 686 lol. The serial # is actually AAC3XXX. Let me know if you need to find out what the other X's are if it'll help.
The Std Catalog is a bit vague with these serial #s. It lists the serial #s for 1981 and 1982 as AAA0000-2100 and AAD2120, respectively, so I'm gonna go for 1981 for serial # AAC3XXX.