Liberia $20 Dollars KM 838 2000 - Battle Of Shiloh 1862

I can tell you why: it's because Liberia was effectively an anarchy back in 2000, engulfed in what is now known as "the second Liberian civil war". With nobody to tell the foreign contracted mints (mostly private mints in America) what they could and couldn't make, the mints used "Liberia" as a flag of convenience to make whatever they darn well pleased. Certainly nobody in Liberia in 2000 would have cared about commemorating a battle in some foreign civil war 150 years ago, they were all too busy fighting their own civil war.

And with no "Liberian government" to ask if any given coin was legitimately authorized as legal tender or not, and with rival factions authorizing their own coinage issues (so they could raise funds to buy weapons), it's impossible to try to figure out which ones were authorized by which faction - if any such authorization ever actually existed, and the mints weren't simply lying about their "coins" being "legal tender".

Some of those mints would have made 31 gram (1 troy ounce) coins, others would have used whatever standard they felt like using. So basically, the two different $20 coin sizes would have been made by different mints. Or different groups of mints, I think lots of not-entirely-reputable mint corporations jumped on the Liberia bandwagon at this time.

It''s also why the series is poorly catalogued, and why some of them end up getting listed in the mainstream Krause catalogue (with KM numbers) and others in the "Unusual world coins" catalogue of unofficial and fantasy coins (with X numbers).

So the true question is not "is it counterfeit" - it almost certainly isn't, since these things are so dubious and obscure not even the Chinese would bother counterfeiting them - but rather, "was it ever really a coin in the first place".