|A106 : by Tony Garland |
The difficulty with this particular Greek preposition [epi] is the enormous variety of uses which it has within New Testament Greek. Thus, one of the foremost Greek lexicons of our day has a very extensive treatment of the variety of uses and shades of meaning conveyed by this preposition—spanning some 3, 8.5 x 11 inch printed, pages (6 columns) of text in a small typeface.
The phrases in question (Rev. 13:16) are:
ἐπὶ της χειρὸς [epi tēs cheiros] [upon the hand], in the genitive case. When [epi] appears in the genitive, it often expresses contact: “on”, as in answering the question “where?”
ἐπιν τον μέτωπον [epin ton metōpon] [upon the head], in the accusative case. When [epi] appears with the accusative it can also be answering the question “where?” : “on,” “upon.”
In Rev. 14:9, the phrases appear in reverse order with the opposite case: [upon the head] is in the genitive case and [upon the hand] is in the accusative case. It would appear that the similarity in the meaning allowed by the use of [epi] in both genitive and accusative cases as well as their reversal in the two passages indicates that the meaning of [epi] in relation to the hand and the head are identical (something we would naturally conclude from a casual reading of the English).
The difference in translation of [epi] by “in” within the KJV vs. “on” by other modern word-for-word translations (NIV, NKJV, NASB, ESV, NET, HCSB) cannot be attributed to differences in the underlying Greek text families followed by the different translations since the Greek manuscripts agree at this point.
Perhaps the use of “in” by the KJV reflects the influence of the Latin Vulgate which has [in dextera manu . . . in frontibus suis].
A Latin dictionary gives the primary meaning of the Latin [in], with the ablative case [frontibus], as “in”. However, it also lists “in,” “on,” and “among” as possible meanings when used in this same case. 
The question as to why Jerome might have chosen the Latin [in] rather than [super] when translating the Greek [epi] is something I'm not qualified to address as it would require a level of expertise in Latin and the Vulgate which I lack.
However, given that the underlying Greek has [epi] and the wide range of subtle variations in meaning possible by this preposition, it is my view that we need to look elsewhere to determine whether “on” or “in” is the better translation.
We have considerable secondary evidence that “on” is preferred:
The mark appears to be a visible mark [charagma].
Other Biblical passages where a “mark” is mentioned infer something which is visible by eye to those who utilize the mark (e.g., Gen. 4:15; Eze. 9:4).
There is nothing in the Biblical text to infer an implanted device. The disruptive conditions at the time when the mark is employed seem to argue against a sophisticated high-tech implanted identifier. (As I mention in my commentary, the mark is the same for each individual and serves as an obvious sign of worship of the beast. If a unique high-tech identification is involved, this would be in conjunction with—combined with—the “number of his name.”) The insistence by some of identifying the mark with an implant is pure eisegesis (reading an external idea into the text) based on the latest developments in RFID (radio frequency identification).
There will be great motivation by the beast-led government to easily identify anyone who lacks the mark. This also lends support for a simple mark that can be seen by anybody. The implication is that those without the mark could be easily identified by others unless they are in hiding.
All things considered, it seems best to understand the mark as being “on” the hand or forehead rather than “in”. Even so, it is impossible to be dogmatic given the variation in possible meanings of [epi].
I'll close with two observations: 1) other characteristics of the reign of the beast are far more reliable indicators of the time and person than sleuthing out the possible ways such a mark may be implemented; 2) the Scriptures teach the imminent pretribulational rapture of the church which, by design, is to cause us to watch for Christ (the bridegroom) rather than Antichrist. I believer that Scripture teaches that the Church will not be present to be distracted by watching for Antichrist. When the time is right, she will follow in the footsteps of Enoch—who is a type for those in Christ:
And Enoch walked with God; and he was not, for God took him (Gen. 5:24).
By the time the flood came, Enoch had already been taken.
 BAGD: William Arndt, F. Wilbur Gingrich, Frederick W. Danker and Walter Bauer, A Greek-English Lexicon of the New Testament and Other Early Christian Literaturea (Chicago: University of Chicago Press, 1996, c1979), 288.
 Cassell's Latin Dictionaryb.