Mystery Card In Apple II+

[flodin@seanews.akita.com (Joe Flodin)]

I have a mystery card in my Apple II+.
It is in Slot 4.  It has a white board, and the only markings on it are 
as follows:
On the lower right corner on the front, it says
     SL5B
      Rev A
On the lower left corner on the back, it says
     SL5A
      Rev A
(these are on the board itself)
 
There are 7 smaller chips with 14 pins, one slightly larger chip with 20 
pins, and one large chip with 24 pins.  This last has a sticker on it 
with this handwritten note:
ISI       (or, unclear)  I8I            (those are the letter i, not the 
number 1)
 2                               2
 
The wiring is very simple.  When I type "PR#4" in Dos 3.3, it gives me a 
screen full of black-on-white astericks, and does nothing else.
 
I haven't seen this card in any other Apple II+ computers before.  My 
wife got this computer sometime in high school (about 6-7 years ago).
 
Any ideas on what this card might be would be appreciated.  It's just a 
little question that's bothered me for awhile...
 
One last thing; on the keyboard, there is a sticker that says "This 
Computer is supercharged with Microsoft Mach 10!" but I've been told this 
was something for the IBM, so is probably a red herring.
 
Please e-mail me at flodin@seanews.akita.com
or if that bounces, post.  Thank you!

Oh, yes; I loaded ProDos 1.1.1 on, and did it's slot check thing, and it 
said that slot #4 was "occupied".  (which was a big help =)  )
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Joe Flodin                         flodin@seanews.akita.com
The Mad Straw Hatter has spoken.  You may resume activity. 
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