I have no idea...no LCIII ever shipped with anything less than a 25 Mhz 68030. Are you sure that its actually an LCIII board and not an LCII board? If its an LCIII board, it will have an FPU socket and one RAM slot for a 72 pin SIMM, as well as an enhanced LC PDS slot. If its an LCII board, it will have solder pads for an FPU socket, but no actual socket, and two RAM slots for 30 pin SIMMs, and a standard LC PDS slot.

Unless by some chance its a prototype, this is the only way I can figure as to how an LCIII would end up with a 16 Mhz '030, since all the boards between the LCII, LCIII and LC475 are completely interchangable.