Gaffed Spindle Tops
Spindle tops are close relatives of dice and are often used in various bar games. Bar games, in general, provide an ideal foundation for scams, because of their loose settings and total lack of regulation. Not surprisingly, most of the popular bar games are gaffed and the gaffs used for perpetrating those scams are often sold as innocent novelty items. These gaffs are not so easy to find nowadays, but up until 1961 they were standard items in every crooked gambling mail-order catalog.
The first photo shows two kinds of gaffed Hi-Lo style spindle tops. These spindle tops are percentage gaffs that work (estimating off the top of my head) about 85% of the time, in favor of the operator who knows how to manipulate the gaff. The Hi-Lo style tops used to be used in a game where the players start by each putting up an equal amount of money into a communal pot and then take turns spinning the top. The number that the top lands on represents the number of "units" that the player takes out of the pot.
Hi-Lo tops are gaffed in such way that they either favor the high numbers or the low numbers. Spindle tops, in general, can be gaffed in two ways. The two Hi-Lo tops shown above are gaffed with two different principles, which is why they look different in appearance.
The spindle top on the left is gaffed in a way that allows the operator to secretly push the pin from one side to the other. In other words, upper side of the pin is the handle and the lower side is the part that the spindle top spins on; so by pushing the pin through, the two sides are switched and the orientation of the top is reversed. One orientation will favor high numbers on clockwise spins while favoring low numbers on counterclockwise spins, and the opposite orientation is reversed. The gaff that influences which sides the top is more likely to land on is the shape of the outer rim; i.e. the parameter around the round (in this case octagonal) edge of the top. The edge between the numeral side and the bottom of the spindle top can either have a hard edge, or a slightly rounded corner. These edges alternate, so that all the low number (for example) have hard edges and all the high numbers have rounded corners. This is reversed on the other side of the spindle top, so when the pin is pushed through, and the orientation of the spindle top is reversed, the gaff functions in the exact opposite way. Without going too much into the physics of the gaff, it should just be mentioned that the gaff only works towards the very end of the spin, when the spinning top loses momentum and the top is making its final one or two tumbles before it comes to a complete stop.
The spindle top on the right side is a more simple gaff and in many respects better (precisely because it is simpler). On any far eight-sided spindle top the edges between the numbered sides must have exactly 135º angles. However, on a gaffed spindle top these edges vary in such way that every other edge alternates between sharp and flat. The principle is simple. When the spindle top is just about to come to rest, the leftover momentum will make it tumble over a flat edge and come to a complete stop as it hits a sharp edge. Once again, since the numbers alternate from high to low, any spindle top can be gaffed in such way that a clockwise spin favors low numbers, while a counterclockwise spin favor high ones. The pin cannot be pushed through, to reverse the orientation of the top, but often these tops are sold in sets of three, consisting of on fair top and two gaffed ones. So, to work the scam, the operator must switch the top throughout the course of the game. This may sound complicated, but in a bar environment any such switch requires minimal skill.
The next batch of spindle tops are called Put-and-Take tops. These are gaffed in exactly the same ways as described above, but the tops bear different markings, because they are used for a different game. The game is called Put-and-Take. Players start by placing an equal amount of money into the pot and take turns spinning. The sides labeled P1, P2, P3 represent the number of units that the player is required to "put" into the pot, while T1, T2, T3 represents how many units the player can "take" from the pot. The star represents "take all" and the circle requires the player to match the pot, in other words, to "put" into the pot an amount of money equal to the current size of the pot.
Below is a clipping from the 1961 KC Card Co. Blue Book, advertising a few types of gaffed spindle tops.