Monsieur rbertalotto
You do have a minor quandary. Unfortunately there are glitches. Some from Colt, some from the Replacants. Colt built the 1860 in ALL of the configurations you mention. Early 1860s had 1851 Grips. Later, the longer Army pattern Grips. Some were made with steel, some with brass, some half and half. Supposedly, "London" Navy's were the only 1851s with all steel Grips (not true).
Now for the really fun part. Pietta pays absolutely NO attention to hysterical accuracy. None. Not at all. Pietta builds lots and lots of Never Never guns (THANKFULLY). Pietta 1860 Frames are mostly 50/50 steel. Steel back strap with a brass trigger guard. Pietta only did a very few all brass frames for the 1860. 1851 Grips are almost all, all Brass.
So: Depending on whether or not you are trying to portray a specific time frame, a specific origin, or whether or not you held your tongue right, an 1860 Grip "Could" be any of those you mention. This should have cleared it right up