AR half shekel, Tyre (or Jerusalem, as per Y. Meshorer), dated 36-37 CE (late Second Temple period, the time of Rabban Gamliel the Elder).
[The members] of Rabban Gamaliel [the Elder]’s household used to enter [the chamber] with their shekels between their fingers and throw them in front of the collector, and the collector would purposely push them into the basket.
(Tractate Shekalim, 3:5)
Throw them in front of the collector. They intended that their shekels would go [directly] into the basket, so they would be used to purchase the community offerings, and that they would not end up remaining with the leftovers.
(Bartenura)
The collector would purposely push them. In the Yerushalmi, the text says, “push them into the basket”. It appears [though] that he pushed them farther away, to cancel the intentions of the givers.
And this is to let you know two things:
1. That a person should push himself to prepare for and do a mitzvah. And even if, in the end, he does not do it, he gets rewarded for his good intentions.
2. The collector was not allowed to purposely collect the shekels that were known to him to be from important people, so that all givers would be equal and that whoever merited to have his shekels collected had them collected.
This is why he pushed the shekels around, so they would be mixed up and no one would be able to tell where his shekel was.
(Lechem Shamayim, by R’ Yaavov Emdin ("Yaavetz"))