Alright...more nerdiness here...
I got the April '82 one yesterday and compared it to the May '82.
There's actually 2 cosmetic differences and potentially one audio..
In the following pics, I have the April one on the right and it clearly has a 'Z' on the circuit board by the wires while the May one does not.
The paint is a bit different, too. The April one has less sparkle to it/more solid in color. It's also a bit brighter...a little bit. I hope it comes out in the pic.
For the sound, I had the second oct. Off and the first Octaver and direct level dimed. Always have to realize that even though they have the same pot brands and variety, pot tapers are not always the same. First off, they had different battery types. The April one had a carbon-zinc which is new but is usually right at or slightly below 9volts while the May one was an alkaline battery usually right above 9volts. Does it matter? I don't know.
They sounded the same..but the April one has slightly more fidelity/transient to the attack of the note.
I find it interesting that even after a month of production there were a couple differences in the construction. The sound may just be me but I think I have a pretty good ear. Who knows.