In 1964, the inserted items were metal coins with player pictures on them. At first, there were 120 coins that looked like this:
The coins were inserted one per five-cent wax pack. However, the packs themselves didn't mention anything about a coin being inside it:
(Image from an eBay auction)
However, the ten-cent cello packs not only mention that there are coins inside, but you can even see their outline on the wrapper:
(This also comes from an eBay auction)
The coins were also included in the 25-cent multi-packs sold through grocery stores. The six packs joined together in cellophane yielded six coins. These packs are shown in this sales sheet from 1964:
(Thanks to John Moran for sharing this great archive piece)
After the 1964 All-Star game, another series of coins made their way into later-series Topps wax packs. Twenty-two coins were made of players from each league, giving the 1964 Topps Coins set complete at 164 coins. In a gimmick, Mickey Mantle's All-Star coin showed the famous switch-hitter batting either right or left.
Among the new series, another white banner has been added to the top saying "1964 All-Stars," with only the player's name in the lower banner. The American League players were given a blue metallic background:
The next "minting" of Topps coins came in 1971. They were inserted into packs again, which were given a graphic down at the bottom of the pack. They must have still been in the planning stage when the wrappers were designed, as the coins are merely called inserts:
This time there were 153 coins, and the most recognizable feature is the band around the player's picture that contains the same info that had been in the small white banner back in 1964. The main difference is that the bands came in two colors:
National League players were given a green strip.
As for the backs, they were so similar to the 1964 coins it might make collectors wonder whether the same people were assigned to produce them or whether they were too lazy to do anything different.
In addition to being inserted in packs of 1971, the coins even had their own checklist card included in the regular set:
1971 Topps Card #161 -- Coins Checklist
Since they were included with wax packages they aren't difficult to complete, nor are they all that hard to locate. However, as oddball items, the coins are usually passed over by card collectors, which keeps their value fairly low.
In fact, the coins and checklist card shown above aren't mine but from my 12 year-old daughter's collection and she's actually done well on the collection as far as what she's paid (being adorable probably helps that). What began as an attempt by hobby sellers Wayne Johnson and J.D. Heckathorn to get her hooked on the hobby (J.D. gave her nearly half the set, asking only for a smile in return, at the 2009 National to "get her started"), she's actually less than 20 coins away from completing the '71 set and is hoping to finish it up soon (If you'd like to help her, her wantlist is included in mine...just scroll down to 1971). She's also interested in finishing the '64 set eventually and may even get started on the separate coin sets Topps issued between 1988-'90.