Re: Precious metal values in Middle Ages...
 

There are other tools online, but like I said the rounded versions are used in GURPS mechanics so if you actually use the precise conversion you'll screw up the compatibility between stats in the metric and non-metric version of GURPS.

Re: Precious metal values in Middle Ages...
 

I would probably go with a middle-of-the road valuation, to reflect that there's a glut of dungeon-recovered and dwarf-mined gold and silver on the market, but that a pouch of purely gold coins should still represent a smallish fortune.

So, perhaps:

Gold pieces (GP) aka crowns or eagles - $20, 50 ~ 9g coins to the GURPS (avoirdupois) pound ($1,000 per lb), may be frequently hacked into quarter bits worth $5.

Silver pieces (SP) aka dollars or thalers or silver pennies - $1, 50 ~9g coins to the GURPS (avoirdupois) pound ($50 per lb), may be frequently hacked into quarter bits or farthings worth $0.25.

Copper pieces (CP) aka coppers or copper pennies - $0.05, 50 ~9g coins to the GURPS (avoirdupois) pound ($2.50 per lb). May

So, starting wealth for somebody of Average or Comfortable Wealth can easily be carried in a belt pouch if it's purely gold, a backpack if silver. On the other hand, a dragon's hoard that weighs a literal ton and needs a wagon or multiple pack animals to get back to town is worth a cool $2 million, which is really quite a high level of Filthy Rich and buys quite a bit of stuff at TL3 prices. It might be difficult to get back to the closest town, but once there it might represent greater wealth than the total worth of said town.

And improvising good wagons or other apparatus for transporting treasure troves back to civilization might be one of the niche roles for a hypothetical Artificer template.

Re: Precious metal values in Middle Ages...
 

vitruvian, there is a VERY big difference between silverpennies and silverdollar/taler.

A silverpenny is a very small coin of approx 2g silver value, and was important during the middle age (TL 3). Weight 1 -2 g, diameter ~15 mm (0.6 inch), thickness ~0.5 mm (0.2 inch). A very small and thin coin.

A german/austrian taler, was a real large coin of 23.3 g silver value. Its main time came in the age of sail (TL 4), and later the spanish dolaro as well as the american silver dollar was minted with a similar weight (24 g).
Weight: 23 -30 gramm, so almost an ounce, diameter 40 mm (1.6 inch), thickness 2,5 mm (0.1 inch). So a big and heavy coin.

Re: Precious metal values in Middle Ages...
 

Historically, absolutely. I was going for a gross simplification for DF purposes (where it would probably be too much of a pain to keep track of two kinds of 'silver pieces'), and mixed up the threads.

Not a complete jest --
 

. . . everything I've read about medieval peasants indicates that while almost all were illiterate they had a VERY keen sense of value and knew when they were being cheated.

Take a look at "The Return of Martin Guerre" for a good look at early modern peasant society -- not much different in values from their medieval predecessors.

"Wot? It's the Renaissance already?" [throws another heaping helping of dung on to the field] "Could have fooled me, lad."