Coins and bars both deliver metal by weight at a stated purity. The differences between them are in cost, recognition and how easily a position can be broken up later.
Coins carry a sovereign guarantee
Bullion coins are issued by national mints, which certify weight and fineness and give the piece a nominal legal tender value far below its metal content.
That backing means a dealer anywhere can recognise a widely produced coin on sight, which shortens verification and widens the pool of willing buyers.
The certification is part of what the premium pays for, alongside the more demanding minting process a coin requires compared with a cast bar.
Bars are the cheaper route to weight
Cast bars are produced by pouring molten metal into a mould, which is a far simpler operation than striking a design onto a blank to coin standard.
They are also made in larger sizes, and fabrication cost per ounce falls as size rises, so a large bar is the least expensive way to acquire a given quantity.
The saving is real but it is spent on flexibility, because a large bar can only be sold whole unless it is returned to a refiner for recasting.
Divisibility is a practical difference
A holding in coins can be sold in parts, which suits anyone who expects to realise metal gradually rather than in a single transaction.
A holding in large bars must be sold entire, exposing the whole position to whatever price exists on the day of sale.
Smaller bars sit between the two, offering some of the divisibility of coins at a lower premium and with less universal recognition.
Recognition affects the exit more than the entry
Buying is easy in either form, because the dealer is the one taking the risk on what is being sold.
Selling reverses that, and the seller then discovers how readily the particular product is accepted and at what discount to the metal price.
Common coins and bars from well known refiners meet the fewest obstacles; unusual formats and unfamiliar marks meet more, and are bid accordingly.
Treatment can differ by jurisdiction
Some jurisdictions treat legal tender coins differently from bars for tax or reporting purposes, though the rules vary widely and change over time.
Where such a distinction exists it can outweigh the premium difference, since it applies to the whole value rather than to the fabrication cost.
The specifics depend entirely on local law, and anyone building a substantial holding is dealing with a question that belongs with a qualified adviser rather than a dealer.