Displayable ASCII Characters go up to something like Decimal 126. The values between 127-255 will display all kinds of interesting things... You'll have to write a little program something along the lines of...

Code:
	CounterA=0
	LCDOut $FE,1
Loop:
	If ButtonUp=0 then CounterA=CounterA+1
	If ButtonDown=0 then CounterA=CounterA-1
	LCDOut $FE,$80,"ASC="#CounterA," CHR=",CounterA,"   "
	Pause 100
	Goto Loop
... just to cycle through and you can then scribble yourself a note as to what's what...

I tend to go through an excercise like this to find out things like Pound (Sterling) or Euro signs, the symbol for Degrees (ie Degrees Celcius) etc... because their table position varies from one manufacturer to the next.