Most likely 5-11% this is what some bearing bronze has in it
I kept thinking 1/5 or 20%... But maybe it was that I was remembering the 5 and it was 5%, and that could be...
If I remeber correctly isn't there a hard and soft bronze bearing material? The harder stuff you need to grease it when wearing on a steel shaft. The softer material you don't need to grease to keep it from wearing on the shaft, even without grease. I coud be wrong about that...
These J&K castings are quite yellow more like the color of brass btw. I've had them for several years, and they don't seem to darken with time, in the corner of my shop anyway.
Lets hope the mold is avalilable, and your able to secure it.
Regards, Kirk