this is a really small question but I didn't know where else to ask, sorry!

for halloween, i'm making my own costume from hand and I wanted to be Napoleon. i've actually just about done with the jacket but my only question is, how did these things button up? I can see theres a seam in the middle of the chest and so I thought there would be some buttons on the inside that are fastened to hold it together(how I was intending to do it) but I've never seen a painting or picture of one of these undone so I have no idea how they work or how they're positioned .

thanks in advance!

https://www.nga.gov/kids/napoleon/napoleon-face.jpg