Identifying ][+ motherboards

[Nels Bruckner <nelsb@comcast.net>]

     Here's a subject that I'm sure many of you have been over (and
over) - How do I identify the age of an Apple ][+ motherboard?

     I just picked up a complete ][+ and the motherboard in it appears
to be older than the 4 other ][/+ motherboards that I have on hand.
I'll post more specific details tonight after I take a closer look,
but the details that struck me when I popped the top today at lunch
were:

     1978 copyright silkscreen above 6502, rather than 1979.
     Extra RAM configuration jumper blocks or DIP sockets (empyt) to
the left of each row of RAM.
     No part number visible on the left-middle (i.e. no 820-0044-x, or
similar, that I could see)
     There is no sticker on the bottom of the baseplate. :(
     Keystwitch / separate encoder style keyboard.

     From my limited knowledge, I'm guessing this make it an
820-0001-06 or earlier.

     --Nels