Z while some military buttons do have steel backed reverses (usually called tinbacks) they are somewhat uncommon. Looking at yours i'll try to tell you what they are starting with the left top and working to the right row by row.
1. eagle and anchor
is a civilian copy of the Federal navy buttons , the navy buttons are exclusively brass backs.
2. great seal
I'm not entirely sure if i see the sunburst over the eagle's head . the button is without the usual rim and probably an older pre WWI Army button 1902 to maybe 1906.
3. Eagle with shield and stars
this is pre 1902 ( somewhere around 1870 to 1890 if i had to guess) and is a little unusual in the sense the eagle is looking toward the arrows and not the normal olive branch. its probably an Army officer's button.
4. Anchor
I'm pretty confident this is a civilian dress button
5.another great seal
1902 and after this one is WWI or WWII era
6. crest or coat or arms
i believe this is also a civilian dress or blazer type button
7.Anchor
another civilian navy copy type of button
and the last item is an insignia but i'm very unfamiliar with military rank insignias
, sorry.