After a meal for nine of us Trujillos at a splendid Santa Fe restaurant, Los Potrillos, where the Mexican food is authentic, I plunked down a tip, all in coins. Well, I suspect the waitperson did some quick math: $2.50 for a meal of about $65, or less than 4 percent.

Inferring I’d left him 10 quarters, the server must have thought, “Este chango es un cheap-o.” So I assured him, “Son dolares”: they’re not quarters but dollars. And therefore I wasn’t such a Señor cusco after all.

But that’s the problem. After buying stamps from the often-out-of-order machine at the Las Vegas Post Office, I ended up with a pocketful of Sacajawea dollars as change. The coins were minted in 2000, to replace the unpopular Susan B. Anthonys of July 1979 vintage.

The design, size and shape of both these dollars are big mistakes. Why didn’t someone ask me? Why didn’t they learn after two fiascos that the new U.S. Presidential Series dollar coin is going to be more of the same?

Sure, numismatists will stick around to collect all the series, from George Washington and the next three presidents, available this year, to Hil or Bill or Barack, in 2016. But because the new coins are almost identical to the previous duds, people won’t use them much, and after the novelty fades away, the only place to get them will be, well, in sometimes-malfunctioning stamp machines.

In Copenhagen last September, I stopped at a yard sale and came across a silver dollar dated 1848. It had a heavy feel, and it was bigger than the current coins, like the silver dollars we used to cherish in our youth. I liked the clang of the coin instead of the dull thud we hear today. Many of us would probably have more of those coins today — containing real silver — if the economy of our childhood hadn’t forced us to spend rather than save.

“How much?” The Danish vendor asked for 60 Kroner, or about $10 American, then told me I could have it for five. At home, my son Stan looked up the coin on the Internet and found values from “almost worthless” to $350 American dollars. But my interest isn’t in making a killing (or taking a beating) on a coin.

Back at Los Potrillos, the act of assuring the server that he wasn’t being stiffed meant that I was calling attention not only to the size of the tip but to the fact that I even left a tip. It’s better to leave a tip without publishing that fact in the local press.

When the Susan B. Anthony coin came around, it featured 11 edges, unlike the many reeded edges that gird a quarter. It honored the women’s suffrage campaigner. The design, theoretically, was to allow the owner to feel the difference and thereby not confuse it with a quarter, as was the case of my Potrillos waitperson. But does anyone have super-sensitive digits capable of discerning those alterations?

I got hold of one of the 888,842,452 SBA coins produced and sympathized with the fellow at the 85 Coffee Shop who inserted a then-new dollar coin into the jukebox, thinking he’d get four times as many songs as with a quarter. The SBA coin jammed up the machine, and the only tunes that played were “Three coins in the fountain,” “Pennies from Heaven” and “We’re in the money.”

The Susan B. Anthony replacement, the Sacajawea, features the assumed image of the Shoshone Indian guide who appeared on the scene of history in 1804 to assist Lewis and Clark on their expedition west. The Sacajawea, also called the Golden Dollar, contains 88.5 percent copper but no gold.

The new Presidential dollars, soon at a bank near you, will have virtually identical dimensions. Sure, the new coin will omit the word “liberty,” as the  Patriot Act has pretty much obviated the need for the word. But the crux is not information or appearance — it’s a matter of size. Most people reaching into their pocket or purse distinguish one coin from another by its size, not what it looks like. If they even elect to carry the Presidential coin, they’ll continue to fumble, confusing the dollar for a familiar coin one-fourth its value.

Remember when a silver dollar was the largest coin in your pocket, and carrying more than two of them usually resulted in your mom’s having to mend your pockets? And when they landed on the sidewalk, the silver dollars sounded like Big Ben at noon?

On another occasion, in a Las Vegas restaurant, we read the notice on the menu that parties of six or more require an automatic 15 percent gratuity (fancy word for tip). There were five of us adults and a new grand-daughter, Celina, three weeks old.

I left a tip, assuming Celina would not bump our number up to six. Yet, when the check (fancy word for bill) arrived, we saw that the “grat” had been figured in. When I asked how many large t-bone steaks our 21-day-old had consumed, how many times the waitress needed to warm the baby’s bottle and how many diaper changes the little one required, the manager explained that the number of guests (fancy word for customer) was “left to the waitress’ discrepancy” (a kind-of word for discretion).

I went back to the table to claim the Sacajaweas I’d left, but the waitress — the same one who counted five-and-a-half people as six — had already used her own “discrepancy” and scooped them up.

It was w-a-y too generous a tip, but as I said, I never much cared for those dollars that look like quarters anyway.