The better restorations have the diodes redone and they are silver with the positive/negative diodes stamped in red and black. It's a date code and they should be relative to the Julian date cast on the inside of the case, and made just prior to the case stamping. Just like an engine stamp versus casting date. The outer case should also have the AC Delco embossed logo. The blank one you asked about has the logo as well (see top right first image)
original embossed logo
original date codes
restored date codes
You asked if the cases can be interchanged and the answer is yes. Later style half cases will interchanged but they are easily spotted as the castings have subtle external differences and can be easily spotted. I'm not sure about the gold colored diodes and can only say maybe they were different in 2nd gens, but I'd reason to bet they were silver too Chuck. Those might have been aftermarket.