Who pays / who bears costs: Coin production and bullion purchases are arranged by the Treasurer (s 4, s 9). The Act explicitly allows Trust Fund moneys to be invested in bullion purchases (s 9), so money from that account is available for the Government to buy metal for coinage; those uses have opportunity costs for the Trust Fund. Holders of coins may bear costs if coins are called in under proclamation (s 8(1)(e)). Private persons who make unauthorised coins or tokens face a monetary penalty (s 6).

What behaviour must change for private parties: Private creation or issue of any metal piece as coin or token is forbidden; contravention attracts a penalty of twenty pounds (s 6). Parties entering money contracts must use the coins that are current legal tender under this Act (s 7), unless they expressly use a different foreign or British possession currency (s 7). Cash payees may refuse coins that are not of "current weight" as defined (s 5(2)).

Legal tender mechanics and limits: British or Australian coins of "current weight" are legal tender: gold coins for any amount, silver coins up to 40 shillings, bronze up to 1 shilling (s 5(1)). A coin below the least current weight specified (by UK law for British coins, or by proclamation for Australian coins) is not of current weight and therefore not legal tender (s 5(2)).

Discretion and centralisation: The statute vests significant discretion in the executive. The Governor‑General can change technical features (design, denominations, weights, fineness, remedy allowances and least current weight), call in coins, and make those changes effective as law via proclamation (s 8(1)–(2)). The Treasurer has authority to commission minting and to use Trust Fund monies to buy bullion (s 4, s 9). Regulations may be made to fill implementation details (s 11).

Implementation, compliance burden, and enforcement mechanisms: Compliance for the public means using legal tender coins that meet the weight/fineness standards set in the Schedule or in proclamation (s 3, s 4, s 5). The Schedule contains precise technical specifications for denominations, weights and fineness (Schedule). Private issuers are deterred by the criminal penalty in s 6. The Act relies on proclamations and regulations for much of the operational detail (s 8, s 11), so implementation depends on executive instruments rather than further primary‑law amendments.

Concrete trade‑offs and incentive points (sourced to sections):

• Concentrated decision power: Executive officials decide denominations, weights and call‑in dates by proclamation (s 8). That concentrates choice in a small group and means practical changes can be made without further primary legislation (s 8(2)).
• Benefit/cost allocation: The Commonwealth (Treasurer) arranges coin production and may buy bullion using Trust Fund money (s 4, s 9). That central funding supplies coinage but uses Trust Fund resources that could otherwise be used elsewhere (s 9). Holders of coins face the risk of call‑in (s 8(1)(e)).
• Limits on private supply and substitution effects: The Act prevents private token issuance (s 6). That channels demand for monetary media to official coinage; parties seeking alternative media for small payments must rely on non‑coin instruments or foreign/British possession currencies where appropriate (s 7).
• Certainty vs flexibility: The Schedule gives precise technical standards (Schedule) providing certainty; at the same time the proclamation power allows the executive to alter technical parameters and call in coins (s 8), trading off parliamentary amendment for executive flexibility.

What is not in the text: The Act does not set out an explicit policy rationale or cost–benefit calculation in its own words. Any claim about motivations or wider public effects is an inference from the powers and limits the text establishes (see s 3–11 and Schedule).