COLT DA 45

I have an older Colt double action marked NEW SERVICE 45 COLT on the side of the barrel and on top of the barrel is marked COLT'S PATENT FIRE ARMS MFG CO. HARTFORD CT. USA PAT AUG 5 1884. It has hard rubber grips with Colt wrote on them. It has a serial # 46xx. It is solid as brand new but has a little bit of light pitting on one side of the barrel and cylinder. Does anyone have an idea as to when this gun was made and maybe a rough guess as to value. It is blued with a 4 1/2'' barrel.. Thanks.