I.V. Brass Buttons

The brass buttons in the photo are a mystery to me. They were found by my husband at a flea market in Missoula, Montana. I have 9 large and 12 small buttons. Some of the small buttons have leather disks attached to them. The backs of some of the large buttons say, “Donnelly M’f’g Co. New York” and others say “Mark Cowen & Co. New York”. The backs of some of the small buttons say, “ Waterbury Button Co.” and others say “Donnelly M’f’g’ Co.” Each button has I.V. and a wreath of 3-leaf clovers. The person he received these from thought they were dated pre-1900 and were buttons for a frock coat, 4th Regiment. I’m not so sure. Does anyone have any history/information on these buttons? I’m stumped! Can’t find any info on them, except that they're on the Waterbury Button Co. site, but no other info is given. Thank you so much for your help.