First, those "tin" pennies were minted in '43 (the year after I was) and AFAIK were low-grade steel. (I'll go dig one out and check it for sauce, though.)
Finally, I doubt we'll see any coins made of wood EVER: First, any wood could be used to make coinage would be double the cost of the sorry monkeymetal they're using right now and second the cost of replacing the presses/dies now used would totally wreck the deal.
(They could just PRINT the "coins" on paper but that's already being done for bills and would kill the vending machine world dead as a pile of rocks.)
Maybe some of those genius' in DC should go get a job actually making something that works before they write any more grand theses on the subject.
Yes to zinc coated steel, they are magnetic. I’ve found a terrible one detecting (any moisture and they’re toasted as park turf crown caps), but a buddy found a nice one detecting in a desert town area once.