That was during a time when a nickel had more buying power. Plus, cashing in fake nickels was worth the effort during that era, nowadays, I'd imagine if someone wants to counterfeit money they're gonna try and perfect a larger denomination to actually make it worth their while.
That brings up an interesting point, I'm sure counterfeiters produce "test" coins before mass producing a bunch of one type. They won't make money on one or several coins, but if they made tens of thousands, that's where the money is to made. Counterfeit money comes in all shapes and sizes.
I happen to think that your assessment is absolutely correct. Casting lines are the result of two molds coming together and for that line on the edge to be a casting line, there would be lines across the obverse and reverse faces of the coin in addition to a matching line on the edge at 180 degrees. Creating a mold requires impressing an authentic nickel into molding material and removing the nickel from that material. You can impress half a nickel into the molding material, but you'll never get it out without damaging the mold. I'll go so far as to say that it would be physically impossible for that line on the edge to be a "casting line". While the OP would certainly love to believe that this is a counterfeit nickel, all the evidence presented so far makes that determination very unplausible if not physically impossible. The expense required to produce such a piece would far outweigh any benefit both from a materials and from a labor standpoint. The art of counterfeiting coins has graduated NOT on the casting fronts but in the die making process where an actual metal press is used. Take a look at Daniel Carr's replica pieces. The counterfeiters art can best be viewed with his coins. He takes a real coin and creates a die pair from that coin. However, even though the quality is superb, the end product is an obvious "replica" or "fake".
As someone who has handled almost 300,000 nickels since the beginning of 2011 (yay, roll searching), I can say that, without a doubt, that nickel is real.
The coin in the OP is environmental damage. I have several of those in my PMD collection from nickel roll hunting. That counterfeit Westward Journey nickel, however, is something! Jefferson looks a bit too much like Washington... And has no neck... and Lewis and Clark are inflatable-rafting down the river. I'd love to have one in my collection like that.
Well, this is weird. Usually someone is on here arguing that their fake coin is real, but here are 2 pages of someone trying to argue that their real coin is fake. lol
Me to.. dig one thats been in the soil for a few years, and it looks very similar. Minerals in soils.. acids.. water... you'd be surprised how bad some coins can look when they come out of the ground even after just a few years.