First... since you are not a civil war relic collector, perhaps I should clarify that when we collectors use the broadly generic word "postwar," it means the relic dates anytime from 1866 through the end of the 1800s. More specifically, in Militaria collecting, the Indian Wars era runs from 1866 to 1897, the Spanish-American War era is 1898-99, and then the World War One era is 1900-1918.
I agree with everything you've been told by Buckleboy, Creskol, and D2. I'll add some info for you on items they did not mention, or were unsure about.
The button showing a small eagle atop a large shield is a New York State Militia button. It has what we collectors call a "wide" flat rim (instead of a narrow one), which means your NY militia troops button is postwar, dating from the 1870s through the end of the 1800s.
Unfortunately, the cavalry crossed-sabers (with a number 7) is definitely a 20th-century Imitation ...for too many reasons to list here. I'll just note the lack of the typical four scabbard-rings, and it being solid-cast "silver-ish" metal instead of yellow stamped-brass, and the fact that there is no
exact match-up for it at:
History of U.S. Cavalry Insignia
You asked for dollar-values:
The most valuable of your
metal postwar items are the Texas and NY buttons, which are worth about $10 each.
The horse-harness buckles are worth $1, if that much.
Regarding the excavated ("dug") civil war era eagle-breastplate and oval US cartidge-box plate ...as with coins, Condition is enormously important. Due to the rim-damage and
heavily corroded condition, the oval US plate would retail for about $50, and the breastplate about $75.
I did not include the 5-point star boxplate in the above list, because it would need to be authenticated by at least three professional dealers as being an Orginal (not a Reproduction) before its value can be determined.
My area of study in the past 30-something years has been metal relics, so I cannot help you much about your non-metal ones. All I can say about them is that they appear to be Original ones ...but I cannot date them specifically enough to estimate their dollar-value.