science

Trade-dollar locket

Trade-dollar locket is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Trade-dollar locket rather than just read about it. In short: A trade-dollar locket, also known as a box dollar or an opium dollar, is a type of locket created from two coins, typically trade dollars, that were hinged together to form a hidden compartment. As trade dollars circulated in Asia in the late 19th century, the lockets were popularly thought to be used to carry opium concealed in the secret compartment.

Key takeaways

Trade-dollar locket belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Trade-dollar locket to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Trade-dollar locket from memory before moving on to harder problems.

Reference excerpt

A trade-dollar locket, also known as a box dollar or an opium dollar, is a type of locket created from two coins, typically trade dollars, that were hinged together to form a hidden compartment. As trade dollars circulated in Asia in the late 19th century, the lockets were popularly thought to be used to carry opium concealed in the secret compartment. An image could also be placed in the compartment of the coin making it a traditional locket.

History The United States minted trade dollars between 1873 and 1878 to facilitate trade with East Asia. Trade-dollar lockets were made by hinging together two such coins to form a compartment, which could be opened by pressing on the lid or edge. As the trade dollars circulated in East Asia, including China, trade-dollar lockets were thought to be used to conceal a small quantity of opium, but an 1896 advertisement marketing one as a "secret locket" suggests that it was not intended for use in drug trafficking. Experts are not sure if the coins were ever used to conceal opium, but the coins were widely used in trade between the United States and Orient which is where the majority of opium came from. An 1893 issue of Donahoe's Magazine described their locket as "a pretty thing to have around" to hide a "dear face which no one else can discover". In 1896, an illustrated catalogue titled Busiest House in America advertised a six-dollar "secret locket" made from trade dollars.

Function When closed the coin appeared to be an ordinary trade dollar. The lockets could also be used traditionally, to conceal an image. An 1896 publication which purports to be one manufacturer of the trade dollar locket suggests that the coin was not used to conceal opium. Coin dealer B. Max Mehl suggested in his monthly periodical in 1919 that a locket could be "skillfully made" out of two coins for five to ten dollars.

References

Illustrations

Worked examples

Example 1 — a first encounter with Trade-dollar locket

Start with the simplest possible case. Write down what Trade-dollar locket claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Trade-dollar locket before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Trade-dollar locket ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Trade-dollar locket

In research: Trade-dollar locket appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Trade-dollar locket in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Trade-dollar locket is common in secondary-school and first-year university syllabi. It links to neighbouring topics 19th-century fashion, 20th-century fashion, Coins, so understanding it makes those chapters shorter.
In everyday life: Look for Trade-dollar locket outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Trade-dollar locket in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Trade-dollar locket means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Trade-dollar locket out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Trade-dollar locket in simple terms?

Why does Trade-dollar locket matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Trade-dollar locket?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Trade-dollar locket.