20% yield is darn good. From the pennies I have sorted (maybe $200 worth, not a lot of pennies, really, and not a lot of excess value certainly, but a fair amount of mind-numb work) my yield is much closer to 9%. My problem is that $25 worth of pennies is a 17 lb "brick" and I am just not wanting to accumulate more than the 3 or 4 of them I already have.
I definitely recommend getting one of those "coin discriminator" thingys for about $20 on ebay. I would NOT buy a full-on Ryedale machine. This (only getting the discriminator part---and, you'll have to fabricate some means of supporting it) does not solve the problem of feeding them into the slot one at a time...but that can be done almost without looking while you're watching TV or something. Although after you look at zillions of pennies, you'll be able to rapidly tell the difference without reading the dates. The old brown ones are clearly goodies, but if you're just looking at "brown" you'll miss plenty of very shiny good ones that look new. Likewise, newer (bad) pennies have a way of becoming corroded (perhaps due to the zinc) that can fool ya into thinking they are old. I find the best indication (without looking at the actual date, and ignoring obvious old brown ones that will jump out at you over time) is the depth of the strike. The older ones had a much deeper, stronger strike. Subtle at first, but again, after you see bazillions of pennies and start paying attention to them, it becomes more obvious.
I vote thumbs down on even thinking about melting. I think copper ingots are kind of a goofy thing in the first place...but there are lots of logistical issues with melting and pouring copper into clean looking ingots, especially when you consider the SIZE implied...you think anyone is going to want a 1 oz copper bar? No...we'd be talking a pound, a kilo, and for that, you need BIG heat. And consider: Copper is between $3 and $4. You would be selling ingots for more than "spot", of course, but do you think you could melt and pour 1 pound of copper for less than $3-$4 in fuel? Yes, in a factory environment, in bulk, but on a onesie-twosie basis, I think not. Copper does not freeze from melt cleanly in air, it tends to acquire a pretty ugly, scabby appearance without a controlled atmosphere. I very strongly believe that the guys who sell clean ".999" (seriously, do you think they really assay them?) copper ingots on ebay purchase odd cut-off pieces of thick copper sheet or copper bus bar and saw it up. They do not IMHO melt and ingotize.
