I was thinking about coins today. I use Canadian dimes to represent Harnic silver pennies. They make a nice visual representation for players. One of the things that suprised me is how light and compact dimes in bulk actually are. It got me thinking about the weight of "real" Harnic coins.
According to Harnplayer (Harnview page 19), the average Harnic silver penny is about 1 dram. This got me doing a little research into weights and measures.
According to Wikipedia:
Note that silver, as a precious metal, uses the Troy pound (with 12 oz) rather that the Avoirdupois or international pound with 16 oz.The troy pound is now used only for measurements of precious metals such as gold, silver, and platinum, and sometimes gems such as opals. Most weight measurements of precious metals using pounds and ounces use troy pounds and ounces, even though it is not always explicitly stated that this is the case. Some notable exceptions are Encyclopædia Britannica (a U.S. encyclopedia for about a century now) which uses either avoirdupois pounds or troy ounces, likely never both in the same article (which would make an awkward system with 14 7/12 ounces to a pound).
1 troy pound = 12 troy ounces = 240 pennyweight = 5760 grains.
A pennyweight was literally the weight of a penny, as adopted by King Henry II (1154–1189). This was a sterling silver penny weighing 1/240 of a troy pound (1.55517384 g).
So, to make things simpler for me, I will use metric grams and then convert back at the end.
4 farthings = 1 silver penny (1d)
12 pennies = 1 shilling (12d)
20 shillings = 1 pound (£1 = 240d)
As a GM, I think the most useful amount of coins to know the weight of would be £1 (240d).
240d x 1.55517384 g = 373.2417216 grams = 0.37kg
1 Avoidupois Pound = 453.59237 grams = 0.45kg
So, £1 (240d) weighs about 0.82 "regular" pounds, or exactly 1.00 troy pounds.
Therefore, a substantial haul of "loot", £10 (2400d), would only weigh about 8.2 "regular" pounds and would easily fit in a small sack. At least £500 (120,000d) of the Earl of Vemion's annual feudal payment must be made in silver. That totals about 410 "regular" pounds of weight and would probably fit in a couple of chests or barrels.
I don't know if anyone else cares about this, but it does challenge my assumption that £1 (240d) was bulky to carry around. In fact my prop bag has over £2 and easily fits into the palm of my hand.
Just a few random thoughts.