Starting a coin collection needs a very careful and organized way of working, requiring the study of rules for handling objects, their storage, and how to check their value — breaking the important rules and not using an online coins value checker often result in the permanent reduction of the coin's collection value and leads to financial losses for the collector.
Mistake Type | Wrong Action | Correct Action | Result of Mistake |
Cleaning | Using acid or scrubbing the surface. | Only use distilled water; do not scrub the surface. | Surface scratches, color change, loss of value. |
Storage | Using soft plastic holders | Using hard plastic holders | Chemical damage |
Valuation | Buying an expensive coin without a certificate | Buying only certified coins with a professional grade | Risk of buying a fake coin or overpaying |
Handling | Touching Proof coins with fingers | Only holding coins by the edge, using gloves | Tiny lines on the mirror surface |
Wrong Cleaning of Coins
Coins are naturally covered with a layer of patina, formed over many years due to the interaction of metal with air and the environment.
Using strong chemicals like acid or normal house cleaners removes this important patina layer, changing the coin's original surface and causing an unnatural shine or bad spots to appear.
Such coins receive the name "cleaned" from expert companies, immediately cutting their money value by a large amount, often 50% or more when compared to a coin of the same age with natural patina.
Also, cleaning coins using rough tools like brushes, erasers, or polishing pastes puts very small scratches on the coin’s surface, these damages being easily visible under a small light.
It is also counted as spoiling the coin, making it unsuitable for serious investment and top-level collecting.
Bad Storage Using Wrong Materials
Many new collectors use materials for coin storage that have active chemical parts, these chemicals slowly destroying the metal over a long time.
Soft plastic albums or holders containing PVC slowly release a harmful gas, this gas reacting with the coin's metal, especially copper and its mixtures — a reaction makes a sticky surface, being known as "PVC disease" damaging the surface.
Therefore, collectors must only use safe materials that do not react with metal, such as Mylar or hard acrylic boxes, these materials keeping the coin safe and stable. Storing coins in simple paper envelopes or cardboard holders can also be bad if the paper contains acid, the acid causing the coin to turn dark or develop large spots.
No Grading and Certification
Buying expensive or rare coins without a certificate from big, known, international grading companies like PCGS or NGC is a very serious risk, causing beginner collectors to overstate their own ability to see if the coin is real or to check its condition.
Official professional grading gives the coin a clear, numerical score, such as MS-65 or AU-58, this score showing the coin's condition using the accepted Sheldon scale — an objective proof of the coin’s high quality, greatly affecting its market price and how easy it is to sell.
In addition, the official certificate proves the coin is real, protecting the buyer from getting a fake.
New collectors buying coins from unknown people or from small online shops without a certificate face a high risk of buying fake coins, these fake coins made only to trick collectors.
No Special Area for Collecting
Many novice collectors start buying coins without a clear plan, collecting random coins from a wide variety of countries, years of issue and types, for example, simultaneously buying ancient Roman coins, Soviet jubilee rubles and modern euro coins.
Try to focus on one thing and only then expand the boundaries of the collection, otherwise you may just get confused and not know what to look for.
Buying Expensive Coins in Bad Condition
Beginners often buy coins that are very damaged, have deep scratches, corrosion, or clear signs of rough cleaning, deciding to buy them because the price is low compared to perfect coins.
In numismatics, there is a clear rule: the coin’s value grows very fast as its condition gets better.
The difference in price between a coin in Very Fine condition and a coin in Mint State condition can be thousands of percent.
Experienced collectors and investors try to buy "the best coin for the money," focusing on coins with the fewest mistakes, these coins showing stable growth in value over time.
Not Using the Right Tools
New collectors often forget to use basic tools, causing them to miss important small details and make mistakes when checking the coin.
Necessary tools for careful checking include:
Magnifying glass is needed for finding very small damages, such as scratches, small lines caused by cleaning, and signs of old repairs.
It also helps with the exact identification of small differences and errors during the making of the coin, these small differences changing the price a lot.
A digital scale and caliper is used for checking the exact weight and size of the coin.
These numbers are key to confirming the coin is real because fake coins often have incorrect weight or size.
Reference books and catalogs cause the collector to wrongly identify the coins, making mistakes in the date and missing rare types, this also leading to financial loss when buying or selling the coins.
Buying Proof Coins with Damage Marks
Coins made by a special "Proof" or "Proof-like" method have a shiny mirror background and a matte pattern.
This special way of making them makes them extremely sensitive to any physical touch.
A "Proof" quality coin having even a small number of these marks receives the category "Impaired Proof," losing up to 70 percent of its value very quickly.
To keep their high value, "Proof" coins must always be kept inside their original, sealed holders, and any touching or handling of them must be completely stopped.
Environment During Storage
Not only the storage material, but also the indoor air conditions greatly affect how long coins remain in good condition, especially coins made of copper, bronze, or low-quality silver.
New collectors often store their collections in rooms where the conditions are not controlled.
High humidity, meaning more than 60%, together with fast changes in temperature, helps corrosion grow, this corrosion being known as "bronze disease" or normal rust on iron coins.
Coins stored in damp basements, hot attics, or near heat sources are at risk of metal deterioration over time.
Perfect storage conditions are stable temperature in the range of 18-22 °C and controlled humidity in the range of 40-55%. To achieve these safe conditions, collectors should use dehumidifiers or special climate-controlled safes.
Making Decisions Based on Feelings
One of the most common reasons for financial loss is buying coins too quickly without thinking — new collectors, feeling excitement during an auction or wanting to finish a collection fast, often pay too much money for the coins.
Paying too much happens when the buying price is higher than the coin's real market value, this real value found by checking the prices of similar coins sold recently. Experienced collectors always set a maximum price limit before an auction starts, setting this limit based on past sale data, and they strictly follow this limit.
Numismatics needs patience, a cool head, and decisions based on clear statistical information, not on strong feelings.
No Checking and Documenting
Keeping a detailed record of the collection often seems like a small, unimportant job to new collectors, but not doing this is a serious mistake, affecting how they manage their money and insurance.
Country, value, year, mint location, and catalog number from a known book
The number score given to the coin or a basic check of its condition
Regular updates of the coin's worth based on new market information
If the coins are lost, stolen, or damaged, without written proof of the buying price and the grade, it is impossible to get the right amount of money from the insurance company or prove the real value of the lost items.