Having come up with my own calendar (Cyclic Calendar), I decided to focus on currency. Many of my initial thoughts were based on the metric system we use in the real-world–I thought that isn’t my own system; it’s just renaming currency. Where’s the creativity? The originality? Then it came to me. The Cyclic Calendar will be important so why not use that as a basis for currency?

28 days in a month; 13 months in a year; 4 years in a Cycle; and 25 Cycles in a century.

So why not…

28 iron munts in a copper din; 13 copper dins in a silver talon; 4 silver talons in a gold zlot; and 25 gold zlots in a gold baal.

28 (munts) is a high number before the next denomination (din) so I decided to also include a half-din in the final calculations.

The next step is to determine the size and weight of the coins in my world. These can be calculated once we know three things:

- the real-world weight of iron, copper, silver, and gold per cubic centimetre:
- Iron: 7.87g per cm3
- Copper: 8.96g per cm3
- Silver: 10.49g per cm3
- Gold: 19.32g per cm3

- the weight (in grams) of an iron munt
- the gram for gram value each of the metals will have in my world

Having researched the weight of British coins (between 3.25 – 12g), I determined iron munts would weigh 6 grams. For gram for gram value I decided on the following ratios (I could have used the ratio 28:1, 13:1 and 4:1, which I will explore another day. This would allow all coins to be the same weight–10 grams to prevent the half-din and zlot being too small–but would mean the value of silver to gold is only 4:1, which seems low historically and in fantasy–unless I can think of a good reason for silver to be so valuable):

Now I had: (1) the denominations 28, 13, 4, 1, and 25; (2) the real-world weight per cm3 of each metal; (3) weight in grams on an iron munt; and (4) fantasy world values for the metals (i.e. 14 grams of iron is worth 1 gram of copper). With these four things I am able to calculate the weight of each coin, in my world:

And, finally, knowing the weight of each coin, in grams, I am able to calculate the size each coin should be in cm3:

After a little bit of further thought I decided I wanted the shape of my coins to also be derived from the calendar so decided on the following:

- Munt: 28 sides-26 sides and 2 faces, which would be almost a circle
- Half-din: 7 sides–5 sides plus 2 faces (7 doesn’t fit the calendar, however, it is half of 13 rounded up
- Din: 13 sides–11 sides plus 2 faces
- Talon: 4 sides–pyramid
- Zlot: 25 sides–23 sides plus 2 faces, which would almost be a circle
- Baal: 1 sides–sphere

This wonderful website allowed me to calculate the size of most of the coin shapes.

Here is a useful link for metal densities.