I've read it was practiced in Egypt, unsure of Eastern Europeans, but from what I understand there is somewhat of a tradition of getting a small cross tattooed on the wrist. The idea being that you would not be able to deny being a Christian in times of persecution, therefore preventing the possiblity of mortally sinning in that regard..and it also served as an identification to know who to allow into Church. I haven't really looked into it that much and am unsure if it was practiced by both Coptic 'Orthodox' and Catholics, or only by the Copts