Dear Ed, 
 
When you say "early banks" how early?    May I suggest figuring out what it  
is that you think banks do.   Once this function is stated then it will be  
fun for all of us to describe institutions as far back as ancient times  
that performed this particular function.  When the  
institution-performing-unit was or was not called a "bank" but those who  
used the instition is then a different and less interesting problem. 
 
Best wishes., 
 
 
L. Moss