Placing spring-type clothespins on a coffee can rim, as well as removing them, is a classic Practical Life activity in Montessori. The activity is geared for those at least 2.5 yrs old, so for toddlers as young as Tyler (19 mos), the old-fashioned clothes pins work best. I found ours in the unfinished wood section of Hobby Lobby.
Deciding to use two hands to push the pin on as much as possible.
We're not coffee drinkers, but this container which was of similar width and did the job. I'm looking to locate a big sturdy coffee can soon. Though not the point of the activity, the pins can only be pushed down so far due to the curve on the bowls, and this seemed to bother Tyler a bit. Otherwise an enjoyabe activity!