Your pistol (38c Combat, it came in .177 or .22 caliber until 1973.) is worth somewhere around $75 and you can add 20% for the original box. The pistol was made in 3 variations first from 1964-73 (Metal rear sight and cylinder) then from 1973-76 (Plastic sight and cylinder) and finally from 1976-81. (.177 version only)
It's a replica if a S&W 38.
Source "Bluebook of Airguns 9th edition."
BTW. It's nice to have someone ask a question with all the information I need to answer it. I get well over 100 questions asking how much is my Crosman 38 (or other model) worth without any other information as to the condition.