18MEX

1. Comes from 1829, not 1830
18MEX (Mark Derrick and John David Galt, 2001-2005) is explicitly based on Francis Tresham's 1829 system, not on 1830. It's for 3-5 players and always uses a fixed $9,000 bank.

2. Mail contract: a fixed income just for owning a train
Every major company has a "mail contract" with its home city: if it owns at least one train at the start of its turn, the bank automatically pays it the revenue value of its home city, on top of whatever its routes earn. This passive income doesn't exist in 1830.

3. A national railroad formed by merging existing majors
In 1830, public companies can never merge with each other. In 18MEX, buying the first 5-train triggers the "NdM Merger": players may voluntarily merge their major companies (only certain companies are eligible) into the NdM (National Railways of Mexico), which receives all of their stations, trains, and cash.

4. A phase with a fractional number: 3½
Once five 3-trains have been bought, "Phase 3½" begins: all three minor companies close at once, and their owners each receive a share of the corresponding major company in exchange. In 1830, phases are always whole numbers, and privates/minors don't all close simultaneously like this.

5. Delayed train obsolescence, not immediate
In 1830, a train is removed from the game the instant the train that makes it obsolete is bought. In 18MEX, once 4-trains become obsolete, they can still be used until after their owner's dividend step on their next turn — only then are they removed. It grants a buffer turn that doesn't exist in 1830.

6. Dividends for unowned shares go to the treasury instead of being lost
If a company pays dividends while it still has shares in the "Initial Offering" (unsold), that portion of the dividend isn't lost: it goes into the company's own treasury. In 1830, dividends for shares nobody owns simply aren't paid to anyone.

7. Half-value certificates (5%)
The NdM has special 5% certificates (half the value of a normal share), in addition to the president's certificate (20%) and regular ones (10%). In 1830, every share of a company is worth the same 10% (except the double president's certificate).

8. Sequential purchase of privates and minors, not a classic auction
At the start, each player may buy the cheapest available private or minor at face value, or bid on it; if anyone bids, an auction is triggered only among those who bid. 1830's initial private auction is simpler and doesn't allow this "buy directly at face value" option.

9. A lower share-price ceiling ends the game
18MEX ends when the bank runs dry, when a company's share reaches $200, or if a player goes bankrupt (which halts the game immediately). 1830's price thresholds and ending conditions are usually different and more generous in numbers.

10. The winner is calculated using the face value of privates/minors, not market value
To determine the winner, major company shares count at market value, but the privates and minors a player owns count at their face (par) value, not what they'd cost on the market. 1830 has no such distinction in final scoring.

18MEX — Schematic summary (vs 1830)

SETTING

• Based on Tresham's 1829 system; 3-5 players, fixed $9,000 bank

COMPANIES AND INCOME

• Mail contract: pays home-city revenue just for owning a train
• NdM: national railroad formed by voluntary merger of existing majors when the first 5-train is bought
• 5% (half-value) certificates in the NdM

PHASES AND TRAINS

• Phase 3½: simultaneous closure of all three minors when the fifth 3-train is bought
• Delayed obsolescence: obsolete trains keep running until after the next dividend payment

STOCK MARKET AND ENDGAME

• Dividends for unowned shares go to the company treasury instead of being lost
• Sequential purchase (or auction) of privates and minors at the start
• End: empty bank, a company at $200/share, or bankruptcy; final scoring uses face value for privates/minors