that break-off thingy corner bit kinda tempts my brain to say that this is to make it zorro1 slot compatible? (A500/A1000 sideslot/car card cage)?
but counting the pins and cut out comes to 12, and 12 off of 100 makes 88. not 86. so ... erm not so sure then...
I've just read the docs (lol). yeah, it's for the 86pin A500 port. either via slot adapter or hand soldered edge connector.