18Ireland

1. Companies start with only 5 shares, not 10
In 1830, every public company has 10 shares from the start. In 18Ireland there are up to 14 possible companies with only 5 shares each (one always in play, another chosen at random); this smaller size is the normal starting state for any company.

2. Mergers — sometimes hostile — to become a 10-share company
Two 5-share companies can merge to become one 10-share company. Shareholders of both companies vote for or against it; even shares sitting in the bank pool "vote" based on whether the merger would raise or lower their value. If the vote passes, the merger goes through even if one company's president doesn't want it. In 1830, public companies can never merge with each other.

3. Different ownership limits depending on company size
The per-shareholder limit is 60% for 5-share companies and 70% for 10-share companies. In 1830 the limit is always a fixed 60%, regardless of company size (which is always 10 shares).

4. Trains rust in two stages, not all at once
When a train becomes obsolete, it first "rusts": it can be bought back from the bank at half price but with half its capability, and stays in play in that reduced state. Only later does it fully "rot" and get removed. In 1830, an obsolete train is removed outright, with no such intermediate step.

5. A much smaller bank
18Ireland starts with a bank of just £4,000, a much tighter figure than 1830's, reflecting the smaller scale of its companies (5 shares instead of 10) and making the empty-bank ending arrive relatively early.

6. Companies can permanently fall behind
The design accepts that some of the 13 starting 5-share companies simply won't thrive (due to under-investment, geographic isolation, or poor founding timing) and will stay behind for the whole game, rather than forcing every company to stay equally relevant the way 1830 tends to.

7. Up to 6 players
18Ireland supports 3 to 6 players, slightly above 1830's usual range (2-6), and the interaction from hostile mergers becomes more relevant the larger the group, since share portfolios end up more spread out.

8. The bank pool's vote can decide a merger
Letting unowned shares in the bank pool "vote" on a merger based on the effect on their own value is a mechanic with no equivalent in 1830, where pool shares are purely passive.

9. Privates close with a specific train (8H)
18Ireland's private companies close when the first "8H"-type train is bought — the game's own reference point for marking the end of the private phase, analogous in spirit (not numbering) to 1830's closing points.

10. Irish setting with pounds sterling
The game is set in Ireland and uses pounds (£) as currency, reinforcing a historical identity quite different from 1830's Northeastern USA.

18Ireland — Schematic summary (vs 1830)

COMPANIES

• Start with 5 shares (not 10); up to 14 possible, one always in play
• Merge (sometimes hostilely, by vote) to become 10-share companies
• Ownership limit: 60% for 5-share companies, 70% for 10-share ones
• Some companies can permanently fall behind

MERGERS AND VOTING

• Shareholders of both companies vote; bank pool shares count too
• The merger can go through even if the president disagrees

TRAINS, BANK AND SETTING

• Two-stage obsolescence: rusted (half price/capability), then fully removed later
• Small bank (£4,000); privates close with the first 8H train
• 3-6 players; Irish setting