Also, that notch in the middle acts as both an orientation key and voltage overload preventer. If you have the 5V, that notch will be about dead center. If it's 3.3V, then it's moved a bit to the left, and will not fit the socket.
Note: at this time, many manufacturers were making chips that ran on either 3.3 or 5 volts - they sensed the voltage, and adjusted automatically. Although mainly used for cache on 486/586 systems, there were a few that made SIMMs using said chips, and they had a wider notch that allowed insertion into either 3.3 or 5 volt sockets.
In short, if the SIMM isn't the right one, it won't fit the socket. Go for it!
banzai
