This is a vintage Sterling silver repousse brooch featuring a Mexican cowboy (vaquero) on a horse, likely manufactured in Japan. 

It is similar in design to other Western-themed sterling silver pins, such as those depicting "Calafia" women riding side-saddle or rodeo riders. 

The piece typically measures approximately 1.5 inches, though exact dimensions may vary. 

Similar items have been identified in pre-owned condition at various price points, often marketed as collectible equestrian or Western jewelry. 

The estimated value of this vintage sterling silver vaquero / cowboy on horse brooch typically ranges from $45 to $95 USD on the secondary market. Highly sought-after or pristine examples sold through specialized historical auctions have reached upward of $250