My .590 shows a very faint small number on the back of the rear cam journal, #911973. It's a 3 bolt cam, has purple paint, a few foundry marks.....and 1.537 over the nose, and a 1.151 base circle.
I was just about to give up looking for it, I thought I knew exactly where it was, and it wasn't. Last time I looked for it, I couldn't find it either, and I bought, and installed a .557.
And of course two weeks later, looking for something else, I found the .590. Oh well.
Found it a little bit easier this time.