I am using many references to Albert’s button book, probably the best resource for US military uniform buttons.His book, the first book listed below, is a must for US military button collectors, as well as various other references on buttons and backmarks.
Note too how the eagle on the Coast Guard buttons (at the bottom) changed from facing left to facing right at the same time as with the US Navy in 1941.
They were beautiful buttons, most had the familiar eagle & anchor, some of the earlier ones had only an anchor.
Some were American made, but there were many beautiful British made buttons too. As quoted on the US Coast Guard website source listed below, “The service received its present name in 1915 under an act of Congress that merged the Revenue Cutter Service with the U. Life-Saving Service, thereby providing the nation with a single maritime service dedicated to saving life at sea and enforcing the nation's maritime laws.
“The shift of the eagle's aspect to right-facing from left-facing is logical from the perspective of heraldic tradition, since the right side (dexter) is the honor side of the shield and the left side (sinester) indicates dishonor or illegitimacy.” (source: the buttons in the picture, those on the left are Civil War-era, those on the right are from a WWII US Navy uniform (my father-in-law’s).
There were two primary types of US Navy buttons worn during the Civil War. They are both “an eagle resting on a horizontal anchor, three cannon balls below, with 13 stars encircling, on a lined field”.