What Is It?

Life is full of mysteries. Some will reveal themselves in time or by chance. A few mysteries you will never know. I have found, in most cases, a mystery is something one just doesn't bother to find out. I am making a conscious effort to solve one mystery in my life which has been tickling my curiosity for years. What is the object below? The person who can give me the correct answer will have my eternal gratitude. You must be able to prove your answer or somehow I must be able to confirm it. More detailed specifications of the mystery object are given below. UFO/Alien theories will be politely ignored.

General Description
Object is a round disk approximately 2.5" in diameter and 1/16" thick with a 0.5" diameter hole in the center. Object is made mostly from an aluminum alloy as the back and edges appear to be aluminum metal. The top is coated with a yellow-brown material that is smooth and hard. On top of this material is a thin etching in a metal that appears to be copper or brass. The etching is on top of the yellow-brown material and is not protected as it is rusting (See picture below). There is an outer and inner circle of etchings. The outer etching is a circle of regular symmetrical patterns. The inner etching has a regular design although not symmetrical and is reminiscent of a fractal pattern. On the back aluminum side near the center hole there is a two line hand inscription. The first line reads 345 or B45. The second line reads P972-5.

I should also mention the object is a bit unusual as it was made at a time when the process of extracting aluminum was expensive. Also, the etchings were made without the benefit of computer aided design. We're talking 1960s technology folks! Home computers did not exist. Or hand calculators for that matter!