The design varied several times and can be used to date the clubs. The more original their condition, the better. If all the grips are the same, it's likely they are original. Also look for markings on the top of the shaft near the grip. Some makers marked their shafts as well.
Original shafts are better.
Nicoll used dots a lot, so it's not too good a way to date their clubs. If the faces are completely smooth, you have pre-1910 clubs, and they are definitely more valuable. Depends entirely on the buyer. Well, that's it for now. Please feel free to email me if you wish, but please also recognise that I too am still on the learning curve.