[RTTY] Upside down

[Gary AL9A]

During the contest I was repeatedly called by some poor soul whose entire 
string was nothing but garbage.  I knew it was the same station each time 
because in the middle of each garbage string were the characters ...s901... 
I could not decode anything and even though I sent several messages stating 
that I could not decode the station calling me he kept calling over and 
over.  This happened several times during the contest and right at the end 
he was the last station that tried to work me.

Being a bit slow on the draw sometimes it finally dawned on me too late that 
the guy might be sending upside down.  By that time though it was all 
history and I couldn't verify my suspicion.  I don't think I've ever run 
across an upside down signal before so I'm not sure what I should have done. 
If I hit the REV button in MMTTY would it then decode his signal?  If he was 
indeed upside down, how could he copy my call and exchange?  If this happens 
again should I tell to other the op to hit his REV button to see if it 
corrects the garbage?  What's the best way to handle this?

73,
Gary AL9A