833 or 833OD (identifying)

One sure way is to actually figure it out.

Your front shift shaft is the 3/4 shaft. You want this in "3rd" gear because 4th is the same straight through gear (4th on a 4 speed and 3rd on an OD.)

BUT 3RD GEAR IS WHAT'S DIFFERENT

So get the box into neutral, then take a wrench, etc, and shift the front shaft CLOCKWISE into 3rd.

Now simply rotate the input ONE turn and see what the output does. If it turns LESS than one turn, it's a 4 speed. If it turns MORE than one turn, it's an OD box.