Although there are other ID-clues, such as the details of the wreath, the "round" ends of that buckle's belt-loops, and their height, are the key clues for identifying that buckle and dating it.
Note that the belt-loops on your buckle are significantly longer (or "taller") than the wreath-circle's diameter.
I searched all through the 616-page book "American Military Belt Plates" for you. It seems to contain no exact match for your buckle. A similar one is shown on page 92, which is an 1830-1838 State Militia buckle ... but its loops are the same length as the wreath-circle's diameter. (Also, the wreath's details do not match your buckle's wreath.)
The book shows two other buckles (pages 235 and 245) which are similar to yours, having round-ended loops which are "taller" than the wreath-circle. The book says they are 1870-to-1910, and were made for civilian bands and fire departments.