I used a baggy and a small cup to soak the whole part with the leaves in the Pb Blaster. I soaked it for over an hour total. I took it out from time to time to try to work the leaves loose one at a time and blow it out with compressed air. I cleaned one leaf with a scrubbie pad but maybe didn't get it clean enough to see numbers if they were there.
I have tried to collect some books on locksmithing but they weren't cheap when I looked.
Sorry if this is not what you wanted to hear. I reserve the right to be wrong, others take the liberty. My posts are not intended to be complete, just enough to help you find your own answers. Don't let the Relevance Paradox get you.