hey,
     Sorry don't know much either other than alot 
(haven't seen any other ones from the original 
show for sale.) I know there were some limited 
editions made one of (speed in the helmet 
driving) one of racer x driving one of speed 
jumping from the car (begining of show) one of 
the whole cast and prices on those ranged 250-700 
depending on what came with them and edition # 
some were signed others had original sketches. I 
would suggest contacting anime-cel.com he has 
some from the origional show in his collection he 
might have an idea. Either way though I would 
love seeing pics of what you got.(attic prizes 
are always cool but even better when its stuff 
like what you said)
                     indy