I can’t help with the number .. but the thingy in the middle is a Gate mark... from where the liquid cast iron flowed into the mold when it was made.
I would put it in the oven on self clean and go to town on it and re-season it!
That gate mark was not important way back then because you would take the ring out of the wood burning stove and the pan would have nothing under it. You could grind a little of it off to make it sit better on your newer stove... or just use it on your grill and enjoy it!
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