How old is a c9a 20 cal crosman pellet gun?

Answer 1

I Think I've located the answer to your question.

A short history. Benjamin air rifles and Sheridan air rifles once were separate companies. Sheridan developed the C9 20 caliber series of rifles. Benjamin bought Sheridan and continued to make the C9 20 caliber series rifles. They also made a .177 and a .22 caliber C series rifle called a Benjamin. Crosman bought out Benjamin (in 1992) and decided to continue making the C series. With the name Sheridan on the .20 cal rifle and Benjamin on the .177 & .22 cal rifle some rifles also had the Crosman name on them. ( confused enough?)

Because you have asked for about a Crosman C9 I believe yours in one of the later models. It was most likely made around 1997-2000.