CONGRADULATIONS!!
THESE ARE HARD TO COME BY, I HAVE ONLY SEEN ONE FOR SALE IN THE LAST 30 YEARS GIVE OR TAKE AND IT WAS A VERY POOR EXAMPLE. YOURS IS FIRST CLASS AND WITH GOOD PATINA AND UNUSUAL TO HAVE BINDINGS IN SUCH GOOD SHAPE. HERE ARE SOME PICTURES OF OTHER EXAMPLES AND FORMS FROM GUYANA BRAZIL.