This oil lamp is displayed in The Allard Pierson Museum of The University of Amsterdam. The Staurogram is similar to the Egyptian Ankh which is thought to signify life or eternity. The Staurogram offers a physical likeness of crucifixion and was used by the early church as a monogram on items, such as this oil lamp, indicating their faith.
Also, the Staurogram was used in early biblical texts as an abbreviation for the word stauros (cross). Early N.T. manuscripts such as the papyri P45, P66, and P75 use a staurogram to physically depict Jesus on the cross at relevant places where the word stauros is used. Other Nomina Sacra were also used as abbreviations in manuscripts, such as the word for Christ and God, but only the staurogram offers a likeness in form of what the word stauros means.
Larry Hurtado gives a great overview of the staurogram in this article: https://www.biblicalarchaeology.org/daily/biblical-topics/crucifixion/the-staurogram/