Here's the specification sizes for this stamping. They are 5 (120mm) by 1/2 (15mm) inches and are lightly dapped for depth. They are raw brass and are ready for a patina or paint. They will oxidize over a period of time, but brush up to bright golden color if you use a steel wool (size 0000) pad on them.
The finish is fine silver plating. I have these custom plated for me by a fabulous company that works with high tech manufacturers. He's more expensive but in the years I've worked with them they've always have a high quality finish.
I could also change the patina or the finish of the piece by using this technique as seen in this video.
https://www.youtube.com/watch?v=iTxrL8tW-qE