Could it be a Sharp SM-series microcontroller? I seem to recall that they came in pretty small packages and were used as security lockout ICs for the NES up through the N64.
Incidentally, although this isn't TMS or handheld-related, if you would be willing to take a crack at torching them to see if they're optically readable, it would be really cool for MESS to up the accuracy ante on Nintendo consoles by actually emulating the lockout ICs. They are in fact microcontrollers, after all. It would also be very helpful for the N64, since the IPL does some handshaking with the lockout ICs. Not only that, the IC that handles peripheral I/O on the N64 is theorized to be a microcontroller - it also supplies the 2k or so IPL ROM, so it would be nice to get that torched and read as well.