Gamma, check out doubledie.com for details on the 1982 DDO
series. The DO-004 is difficult to distinguish, the main pick up on this one (zinc version) is the I (super fat) B bumps on right and R bumps on right of Liberty. I have pics loaded of a possible do-004 zinc on an older post. The consensus is mixed on if my example is in fact the 004. I believe the 1982 zinc has matter hub die doubling as I have about 12 like yours and chucked about 50. The one I posted is the only one that may actually be a 004. Tough variety to distinguish for me, good luck. Hope yours is but I'm seeing just thick master die doubling like the dozen I have in the closet.