Typical 5 speed freewheel for multi use was 14-16-18-21-24. This is what I rode on two old 5 speeds. My 80's 6 speed freewheel was also 14-24 but I can't remember the jumps... Maybe (14,16,18,20,22,24?). I am looking at a 70's typical racing 5 speed right now (Regina Oro) and it is 13,14,15,17,19. My 80's 6 speed freewheels are 13-23 and 13-24 but I can look at you right in the face and tell you that I NEVER use the 13 cog for anything, even downhills, but with my 52/42 chainwheels I consistently use the 52/17 and 52/19 for level ground and the 42/19 - 42/21 - and 42/23 or 42/24 for climbing hills. I have absolutely no idea what anyone does with a 53/12 considering the world's hour record was set with 52/14! I think the 11 and 12 cogs are used mostly for massaging one's ego or 45 plus mph going downhill.
Garth Libre in Miami Fl.