In P.Col. 11.294, an amulet with the text of a prayer and a citation of Ps 150, there is an interesting nomen sacrum (with overlining) for "Abraham" on the verso, l. 11:
This is one I haven't seen before. It seems to be an abbreviation of Ἄβραμος, the spelling of which is attested. The editor (Timothy M. Teeter) notes two other possible occurrences of the nomen sacrum in P.Bodmer VII 12.14 and P.Bodmer VIII 49.12. Otherwise, this may be the only example. One thing I have learned from my study of Christian amulets is that scribes wrote nomina sacra--among other things--in strange ways. They were rarely consistent in employing abbreviations and supralinear strokes. In one line, for example, you will encounter a sacred name in abbreviated form and then in the very next line you will see it written in scriptio plena. My forthcoming dissertation (which I am presently wrapping up for good!) documents many of them. So, an unusual nomen sacrum is not a strange thing in amulets. In any case, I'm wondering: has anyone else encountered an example of a nomen sacrum for Abraham, other than those mentioned above? Teeter published his edition of P.Col. 11.294 in 1998 so perhaps another example has appeared since then.