There have been a few posts lately where people talk about using silver standards in their games rather than the default gold standard for coinage/prices. I'm too lazy to look them up right now (too many other links below). They're not rare, hard to find things, though, so I'm sure most of my readers have at least come across one or two before in the past.
Now, first off, there's nothing wrong with doing this in my opinion. You just switch a few notations, and decide which items on the equipment list will still be priced as-is in gold (usually armor, mounts, ships, castle construction costs), and everything else gets the same number but read as silver, rather than gold.
It's more 'historical' because most historical coinage was silver, not gold (although most historical transactions were barter/trade/credit affairs, from what I understand--this is all beside the point, however).
So what are some reasons to stick with the game's default assumption of a gold standard currency?
I've been thinking about this from two lenses. One is the recent posts by ckutalik and Trollsmyth about here and here. They discuss the inherent anachronism of the 'standard D&D setting.' The game is set up to purposely distort the historical influences, as it seems.
Second is the old idea of trying to figure out interesting setting details from oddities or curiosities found within the game text, inspired by this old post on The Forge by Rich Forest (Superhero Necromancer) and Ben Lehman, which I've blogged about before.
So, what does the way D&D is written, with gold coins being the default currency, tell us? What other game assumptions influence this?
First off, the basic premise of the game is that there are monsters living in the wilderness or in dungeons, and those monsters have amassed treasure. This is an influence that comes from old Norse myths and legends, where kings would be buried with treasure hoards*, and then legends would spring up of monsters protecting these hoards. See the dragon episode of Beowulf, or the Volsung Saga/Nibelungenlied for two classic examples of this. Tolkien popularized this in The Hobbit (not so much in Lord of the Rings).
How the monsters get the treasure in D&D is not explained, though.
Next, adventurers go out to take that treasure from the monsters. This is an influence of the Pulps, primarily. Fafhrd and the Grey Mouser adventure because it's in their blood to do so, but their objectives are usually treasure. Again, The Hobbit also gives us a good reference for this aspect of the game.
Now, the final assumption of the rules is that because monsters have all this gold, and adventurers are out there killing monsters and taking that gold, that gold is the standard coin of most realms. Gold flows into civilized areas not from mining operations, but from adventurers looting it from the monsters (who aren't given any source for the gold, leaving it for each group to make up as they like).
And so we have a gold standard in D&D. And while it isn't realistic in a historical Earth sense, it does make sense within the premise of the game.
So what insights can be drawn from this?
First, gold is probably much more common in a D&D world than it is in the real world. There's more gold out there, so it's not as much of a stretch to see gold as the default coin metal. Or if it's not more common of a metal geologically, it's at least easier to get at, because of all the subterranean races carving out dungeons and lairs and cities beneath the surface of the world.
Second, do rulers bother to mint their own coins? With the massive influx of old specie coming up from the dungeons, why bother with making their own? I'd guess that yes, they do still have mints, where they melt down old coins and re-stamp them. This would be done for the same reasons it's done in the real world--to assure people using the coins that they are of the value the government says they are, and to prevent counterfeiting. There's likely a lot less gold mining going on, though. Why take all the effort to mine or pan for gold 49er style, when you could just send a team of experts to kill a basilisk instead?
Third, could gold have once been plentiful in the world, but is now disappearing? Creatures like the rarely used aurumvorax, portable hole+bag of holding disasters, wizards building planar strongholds...there are likely a lot of ways that coins and gems and stuff are disappearing from the world. Could that make gold more valuable again? If you want a good verisimilitudinous fantasy reason for a silver standard, why not consider something like this? Adventurers go for the gold because everyone else is running out?
In conclusion, I'd argue that there's nothing wrong with using the game's assumed gold standard in your game. If you want to switch to a silver standard, that's fine, but historical precedent is not necessarily relevant to some of the game's base assumptions, while the gold standard it presents does seem to have a logical basis within the game world.
* Other cultures have buried kings or other important people with grave goods/treasure, but I've come across few legends of monsters then coming to claim that loot as their own, and heroes then coming to slay the monsters in other mythologies.