As you can see, A.J. pasekens like the first view quoted by Rabbi Levj in Yerushalmi Megillah פרק א הלכה ט, instead of the Bavli Shabbos דף קד:
אמר רבי לוי מאן דאמר לרעץ ניתנה התורה עי"ן מעשה ניסים מאן דאמר אשורי ניתנה התורה סמ"ך מעשה ניסים
Rabbi Levy said that according to the view that the Torah was given in r'tz script (paleo-Hebrew), the 'ayin stood by a miracle. According to the view that it was given in ashuri script (the square antecedent of modern Hebrew), the samekh stood by a miracle.
In both scripts the letter in question looked very much like this: ס, the point being that the Ten Commandments were carved clear through to the other side, so the little hollowed out center could only have stood by a miracle.
א"ר חסדא מ"ם וסמ"ך שבלוחות בנס היו עומדין
Rabbi Hisda said that the mem and the samekh stood in the Tablets by a miracle.
The point here is that all instances of the final מ, twenty-two by my count, which look like this: ם and ס, two of them by my count, stood by a miracle. Clearly this opinion regards the script of the Tablets as the present Hebrew script (the second opinion mentioned in the Yerushalmi).
So A.J. holds like the first view.
In any case, what's written on his tablets? Firstly, the very first word of the Ten Commandments, I, אנכי, is the first word on the tablet on the left. I imagine most of us would picture the tablet on the right, seeing as Hebrews reads right to left. The first word on the other tablet is Honor, כבד, which means it is the sixth commandment. Rather strange, since apparently no tradition has Honor thy father and thy mother as the sixth commandment. Really, Wikipedia says so.
It's not so interesting who designed it, as what was the designer thinking?
Well, I thought of a more famous instance of paleo-Hebrew in popular culture, the Ten Commandments in The Ten Commandments (see). Indeed, it is clear that A.J.'s cover was modeled on that prototype. Aside for the fact that Charlton Moses held them correctly, the text is exactly the same (if not the font).
For the record, here is the text just as it appears in the classic 1956 film:
את אביך ואת אמך
לא תען ברעך
לא תחמד בית רעך
לא יהיה לך
לא תעש לך פסל
זכר את יום
The second thing is the orthography, which does not match the massoretic text. For example, Massoretic תַעֲשֶׂה is written defective as תַעֲשֶׂ. The same for זָכוֹר vsזָכר and תַעֲנֶה vs תַעֲן. It's possible that whoever wrote down the commands for the prop department deliberately left these words defective on the theory (and evidence) that the earlier one goes in Hebrew the less words are spelled plene.
This post took me ten minutes. No, really.