This means that no intelligent person would want to pay for a collector's coin at its collecto's price and then take a loss on it as he trades it as currency.
With that in mind, any business that wants to promote gold or silver trading will probably want to promote a trading coin.
Perhaps the most famous of these right now are gold dinars and silver dirhams minted by the World Islamic Mint in Dubai due to their meeting a high standard of uniformity (always at a weight of one classical mithqal or a multiple thereof) and security features and being sold at a moderate price above spot value.
Coins minted by national mints, though highly standardised (usually as an ounce, a fraction of an ounce, or in grams), are not quite as tandardised due to it being less convenient to calculate between fractions of ounces and grams and multiples of those, ounces and grams being independent measurements).
Of course a business could simplify things by promoting coins marked in grams only or ounces only.
This still leaves the problem of coins minted by national mints being collectors' coins.
A business could turn to other bullion coins minted by private mints, but even then it would want maximum standardisation and security features built in. The only ones I know of that meet that standard are the gold dinar and the silver dirham and their multiples.
Another option is gold-backed crypto currency. I think I read about one also based in Dubai whereby one unit is backed by one gram of gold, making it more reliable than Bictoin for instance. While that's fine online, we still need a physical coin for offline trade. The World Islamic Mint also allows the purchase of e-dinars backed by gold dinars. I believe e-dinars can be broken down into fractions too.
One potential pitfall with the gold dinar and silver dirham are their close link to Islam.
However, I don't see why a private non-Muslim mint couldn't create a secular version of the gold dinar and silver dirham that could be traded for their 'Islamic' counterparts a a rate of one for one but without the Arabic text engraved in it.