Japan mint sets

do Japan mint sets from the 70s damage coins?

  I have a set and its verdigris like this, http://www.ebay.com/itm/1975-JAPAN-MINT-UNCIRCULATED-5-COIN-SET-/161196922633?pt=US_World_Coins&hash=item258815d709

  Mine is 1979, is it worthless?

  I also have a 1877 1 sen with a die error. There is a raised portion of metal but the design is on it also.
  F or so, is it worth more?

Not verdigris but PVC plastic residue.

Acetone should remove it, but it's nasty stuff and you'd have to break up this ugly set. Boo to you, Japan

Be careful handling the verdigris or the revenue on the coin. I would recommend gloves.

Is it worthless? anyone want it?

I'll have it if you don't want it. We can swap.