No expert on these planters just learning myself but the parts book shows that the 102 and 106 were 30-inch wheel planters. the 104 was a 36-inch wheel planter.
The 102 and 104 Had the check rower. Also some of the furrowing attachent were avilable for some but not listed for others. Like the single disk opener was available for the 102 & 106 but not the 104. Same with the double disk opener but then they had a double disk opener that attached to the sword that was available for all three units.
As I stated I'm still learning so I don't know if this was any help or I just confused the question even more.