Men's garments are always a challenge when they are this old. It appears to be a lovely wool flannel or similar wool (not the flannel of modern times) with silk ? embroidery and a cotton or linen back. I am most familiar with this embroidered wool as used for infant's and children's robes, cloaks, etc. in the mid to late Victorian era. While I can only guess at the date, I feel it is late Victorian era, possibly mid Victorian.
It is really a special looking vest. I also wonder if this was for wedding, worn by the groom?
Can you show the buttons, or describe them front and back and tell us what they are made of? Do you think the buttons are original to the vest?