#1, 3, and 4 are Ford script.
#2 is not.
One of the Ford script ones is an odd-ball.
Look close to see which one.
What is it from? Fordson? or?
Look at the timer evolution article in the encyclopedia: http://www.mtfca.com/encyclo/S-T.htm#timer
Ford was constantly experimenting and making changes during production, so it's a wonder so many we find today looks similar
It appears that #3 has it's slot for the retaining pin on the opposite side. Almost like it was intended to rotate in the opposite direction from normal. A couple of years back, someone was talking about a twin T engined tank. Were its engines counter-rotating?
That was my first thought too, that #3 was made to turn backwards. A recent forum post mentioned a couple of people setting up engines to do that. But has it been done enough to cause the regular manufacture of a backwards roller?
Hal & Steve are on the right track. #3 is backwards.
But we are not sure why. It is Ford script.
It does not seem to be modified much except there is an extra notch (red arrow) maybe put there with a hacksaw?
The other notch (blue arrow) seems to be factory stamped.
The roller is also further out (purple arrow) than the rest.
Also, the rivet pins are flat compared to the others.
This part makes your arm tired when getting the engine to run for the first time.
This is a real mystery. Either Ford was experimenting with pushing the roller, rather than pulling it, or else it was for an engine that ran the opposite direction.
So why run an engine in reverse?
Twin engine boat with counter rotating props?
Twin engine tank with counter rotating engines for driving the tracks?
Twin engine Pietenpol?
Safer starting for right handed people?
Maybe its a RHD timer roller for British production?