Maaser Sheni 4:9-10

Ma’aser Sheini 4:9

If one finds a coin, it is assumed to be secular, even if he finds a gold dinar among coins of silver and copper. If a person finds a piece of pottery with the coins and “tithe” is written on it, the coins are assumed to be tithe money.

Ma’aser Sheini 4:10

Let’s say that a person finds a container with “offering” written on it. Rabbi Yehuda says that if it’s pottery, the container is assumed to be secular and the contents are an offering. If the container is metal, it is assumed to be an offering but the contents are secular. The Sages disagreed with this last point, saying that people do not typically put secular contents into a sanctified container (and therefore both are to be treated as an offering).