old glass bottle

Bottle found next to a Civil War burial monument over run with growth and weeds. Clear glass bottle is 8″ tall, lower half is hexagonal in shape. Bottom of bottle is round and 2″ in diameter. Top of the bottle is 1″ in diameter. A letter F on the bottom of the bottle. The numbers 435 across the bottom edge of the bottle. The Civil War captain buried there died in 1885. If anyone can identify what kind of bottle and approximately what year(decade) it may be from.