I was wondering if there's a surefire way of telling if an IBM-PC has its
original motherboard, without opening the case. I saw one at the
Salvation Army today and was considering dragging it home (though I
decided to take another machine instead).
The machine did have a cassette port in the back, with a femal DIN
connector. Is this attached to the motherboard?
Yes it is. So it sounds like it's original.
There were 2 motherboards, a 16-64k and a 64-256k. The former was the
original one. The latter has a B in a circle stamped on the back plate.