Sorry, can't help with a value but you have an extremely nice Colt revolver in excellent cosmetic condition, which I suspect would bring a good amount of money. It could not have been shot or handled much to be in such great shape. The experts in value will hopefully be along soon.
Your New Service looks to be in excellent condition with a set of custom made stocks. I assume that you have a Colt factory letter since you know the exact shipping date. I would put your gun in the $1800-$2400 range. If you were looking at selling it you may do better to find a set of original stocks for it and include the factory letter. Many collectors want a high condition gun such as yours in original condition. The custom stocks could then sell on e-Bay where they should do very well. I hope this helps.
Sometimes oversized grips such as those that have been on the gun for a long time, tend to leave an "impression" or print in the blued finish that may show if original grips are used. A quick check will tell. Very nice NS and Grips look to be a forerunner of later Colt Target Grips of OM post war revolvers. the Jackson