Growing up outside of New York City I was quite familiar with reading that my orange juice or some other food product was "kosher for pesach." I also remember seeing other products with a circled "u" followed by “parve.” The circled U is a trademark of the Orthodox Union, which is one of the biggest certifying agencies for the Jewish community. Parve means it's "neutral"----neither milk nor meat. And that is how my Jewish friends knew that they were able to eat or drink something since it had been declared kosher.
But this is not a new system. A in a recent press release by the Israel Antiquities Authority reveals that a bread stamp with a menorah was discovered in Acco. Here is a bit of what the report has to say.
The tiny stamp was used to identify baked products and it probably belonged to a bakery that supplied kosher bread to the Jews of Akko in the Byzantine period. A ceramic stamp from the Byzantine period (6th century CE) was discovered in excavations the Israel Antiquities Authority is currently conducting at Horbat Uza east of Akko, prior to the construction of the Akko-Karmiel railroad track by the Israel National Roads Company. This find belongs to a group of stamps referred to as “bread stamps” because they were usually used to stamp baked goods.
The stamp is engraved with a seven-branched menorah atop a narrow base, and the top of the branches forms a horizontal line. A number of Greek letters are engraved around a circle and dot on the end of the handle. Dr. Leah Di Segni, of the Hebrew University of Jerusalem suggested this is probably the name Launtius. This name was common among Jews of the period and also appears on another Jewish bread stamp of unknown provenance. According to Dr. Syon and Gilad Jaffe, “This is probably the name of the baker from Horbat Uza.” Horbat Uza is a small rural settlement where clues were previously found that allude to it being a Jewish settlement: a clay coffin, a Shabbat lamp and jars with menorah patterns painted on them were discovered there.
You can read the whole report here. As well as download more photos.