As per ANSI A117.1-2003, 904.1: This window shall be at 36” AFF maximum AND the accessible portion shall extend the full depth from front to back (no visual obstructions or bump ups). It can permit either a parallel approach with this portion being 36” in width, or it can provide a front approach with knee and toe clearance. Either case is OK.As far as a check writing surface, ANSI A117.1-2003 904.4.3 is a sub heading of 904.4 “Checkout Aisles” (Grocery Store Checkout) and is not really applicable. But if a shelf was provided, it then should meet work surface height of 34” AFF for a parallel approach
Also 43" AFF for a vision panel only applies to doors and sidelites to doors (ANSI 404.2.10), not to customer service windows... this is section is a sub section of 404.2 for Manual Doors