These are very elegant ribbed horn oarlocks. They would be right at home on one of John Welsfords Joansa's, or any rowboat, for that matter.
The alloy is an engineered high class brass for increased durability and corrosion resistance. The chemical composition of this brass is close to 464 Naval Brass with the addition of aluminum and nickel.
These oarlocks come with a pin that can be run through your oars to capture them. Note: you must use a ballpeen hammer to rivet the end of the pin so that it stays in the oarlock.