It's a 1944 Japanese coin made of a tin. These don't survive well, and are often corroded. This is raised 'bubbles' though. The oxidized striations are very typical...but not this irregularity. I've seen photos of gas bubbles but not on a weaker metal like tin. Could you see something like this on a planchet--both sides and all these small bubbled areas? Seems like maybe a post mint heat application vs. mint made. Very curious as I've not seen one like this before.
Woody as in wood grain-like? I see the toning/oxidation like this...and a poorly mixed alloy would make sense for that too. It was 1944 Japan and resources were pretty low by then.