It is a modern-era blazer button, a version of Fashion button. Note the remnants of shiny black paint still remaining around the motto's lettering. The motto, which is in Latin, basically means "God Is Our Hope." An alternative translation is "Our Hope Is In God."
To view proof, do a websearch for the motto "Spes Nostra Es Deus". You'll see several other specimens of your button.
I did just that ,,, it seems this button has the wire loop type fastener on the back. I thought it was older...
thanks, the newer ones have a sort of larger square blocky fastener, I'll post the backside. this button is wet in the picture.
"I came across your website when I was trying to find the meaning of the Latin motto on the buttons of a sweater that I bought just a few years ago at a thrift shop. The sweater was made in Calgary ca. 1960’s or 70’s so the buttons are almost definitely reproductions. They do not have the type of slot backing that your photo depicts. Instead they have the more substantial loop that forms the back of the button itself. I believe that the photo shows an original, and my sweater buttons (and also Chuck Williams’) are modern."