The letter/number combination on the butt is the serial number, which in this case (i.e., with an "ABY" prefix) indicates that your gun was produced in 1983 and is a "no dash" - the 581 was first produced around 1980/81. Most, perhaps all, of the remaining stamped numbers are so called "assembly numbers" used to keep track of fitted parts when they need to be separated during production for various reasons. They have no further significance.
You may want to check where the model number and serial number are stamped on the frame in the yoke cutout to see if your gun has the "M" stamp that indicates it was modified in response to the recall of these and similar models. There are number of threads here, including one running currently with regard to a Mod. 686, that discuss this recall so I won't get into it here.
