It's also available as a Vault Video Download.

Tom:

Thanks, Can you give me the contact info for "Vault"

John

The Vault is just a general name they use for the old video series. Here's the link for Penguin, but if you have a favorite magic shop that offers downloads, they'll probably have it too.
https://www.penguinmagic.com/p/S27640

Compulsive that I am, and for the record, I did a bit more math:

Quarter = 0.955 inch = 24.26 mm
Half Dollar = 1.205 inch = 30.61 mm
Same Ratio Up = 1.52 inch = 38.62 mm

A silver dollar is only 38.10 mm.

But we’re looking for a coin that is bigger than a half, yet smaller than a dollar — right? (The proverbial “75 cent piece.”)

So am I not doing something right, mathematically speaking, when the whole idea is to have a special coin that is "larger than the half dollar in the same ratio that a half dollar is larger than a quarter"?

I am confused.

Thanks Tom.
I like the structure of the routine.

John

Karnak, I think it boils down to it being easy to feel the difference between the half and the chosen coin. I got slightly different measurements, but coins and dates can put sizes all over. IE the Canadian Silver Dollar I have is 35.9mm. That's about 6mm difference between a quarter and a half and the half and my Canadian Dollar. Easy to feel the difference. The Piso I have is 33.4mm and it's tough to tell the difference between the half an Piso. I don't think math needs to be involved. Just the spec thinking he's got a half and an quarter in his hand, when he's really got a half and a (insert your favorite coin here) in his hand.

Yeah, it’s one of Roth’s easier tricks to do but a solid fooler. And Tom is right, nothing complicated here, just a quick fooling of the mind as to two of the five senses, sight and touch. Getting the right size coin is usually the biggest trick of it all. 😁 That has probably stopped more people to date from doing this little gem than anything else. 😊

It is the old peso.

Mexican circa 1958.

It’s not just the diameter of the large coin. It also has to be relatively thin.

Reviving this thread. I used to have the same commemorative Jean Paul II Vatican coin that David also used, but can't find it anymore. I looked it up, and that seems to have been 35 mm (if the ones I saw on E Bay are the ones that David and I had). I have the Mexican 1 pesos coin, 1958 (actually have several that are the same going into the 60s), that I looked up as 34.5 mm. Other 34 mm coins are the 1966-1979 and 1974-1980 Bahama dollars, and there is a 35 mm 2 dollar bahama coin (1989-1991).
I see references to a Canadian dollar, and when I looked up the size (1935-1967) that was 36.06 mm.
So my question is, has anyone had success with any coin other than the ones mentioned in this thread, or which from here have you used with success? It seems to me that the Canadian dollar might be a tich too big, and the best size might be 34-35 mm. I haven't tried the trick yet, since I only have the mexican 1 peso coin (34.5 mm), but that seems to be a good size. The Philippine Piso coin I have is a bit smaller, but perhaps the older coins were a bit bigger. I can't find a reference on a google search.

I'd have to do some research again, but as far as I recall, both the Phillipine Peso and Canadian Voyageur had different sizes based on the year. I think the Peso was 38 and 36 mm, while the Voyageur was 36 and 34 (33?)mm.
Edit (did the research):

The Peso existed in 38mm (the size of the US dollar coins) from 1903-1906 as well as a 35mm version, from 1907-1912. Both were predominantly silver, with slightly different compositions.
(If you go further back in time, there was also one at 37mm minted in 1897, but that's likely much harder to find.)

The Voyageur existed in a 36mm silver version from 1937-1966. They then switched to a ~32mm nickel one from 1968-1976, at which point they discontinued it for the Loonie.

There are, of course, other similarly sized coins as others have mentioned. But they also vary in availability.
These also all vary in thickness, which I know can be important to the routine. I recall the nickel Voyageurs were relatively thick, I can't remember on the Pesos.

I think that the 35 mm coin is probably ideal. Anything bigger might be too big. I used the mexican 1 pesos coin (34.5 mm) and that worked just fine. Not many people do the effect really because they can't find the coin (or looking for one is a bit of a hassle).

I went back to refresh my memory of this routine, and had two additional thoughts:

1) Everyone's talking about silver (toned) coins, but since it's never actually seen by the spectator, it doesn't actually have to be. That opens up a lot more options in terms of coins. I suspect it doesn't even need to be a _coin_. A long time ago I remember getting some 34mm washers at my hardware store to practice with, which worked great. There are ones with larger holes (~1/2 inch) - which have the risk of the spectator accidentally noticing in their hand as they separate the two coins - but also ones with much smaller holes, and those tend to be thinner, too. At the very least it's something to experiment with.

2) While the original routine took away the larger coin and left the spectator with the smaller (that's then changed) into the half - I it seems like you could use a similar principle to either do one size smaller (the half is the extra coin) or alternatively get them to hold on to the "half" returning to you the "quarter" that's really something else. Of course, I haven't tried the latter on anyone yet - I only just thought of it - and so it's possible that folks are more familiar/discerning on the smaller coins and it wouldn't work as nicely. Has anyone experimented with that direction?

The math looks okay, so find a slightly larger coin and disregards the "smaller than a dollar" statement.

Years ago, for some reason I misinterpreted the routine as using a dollar coin and a half dollar - and asking them to hand me the smaller coin... probably imagining they would be so familiar with the size of a quarter that they would not accept a half as a quarter.