Ok thx for this additional information and the clarification on the markings. I'm stumped but will move your thread over to a different subforum where we put things that we don't know what they are. Hopefully that will get some good eyes on it.
Also, as to soaking/cleaning, definitely hold off on that step for now. The surfaces are a wonderful brown and it would be a shame to change that.
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz