Is it a real 1969 "gts" ????

Hi,
I am looking at a 1969 dodge dart thats for sale.
The vin is LS23P9B******
I have looked at the GTS registry and these #'s match lots of the ones that are on there.
I believe its the "S" That makes it a GTS or does anyone have any other info ?
Lots of other stuff indicates its a gts, the owner claims he doesnt know.
Im just trying to do my homework so I dont get burned.
Thanks