The higher axle brackets would be either a Model 1 Rotomo or a model 3.They were the only two bases that had the bigger axle bracket size.The model 2 and 2a had the smaller more common size that we are used to seeing.
This one would be the Model 1 & Model 3 bases only.
[Linked Image]
These are the more common ones we see.For Model 1,2,2a.I'm not entirely sure if there were model 3 with this smaller size.I've only had 2 model 3's and both had the larger brackets.
[Linked Image]
I hope this helps.I'm sure it does,now you have to remember that there is nothing about this on paper,but this has come from about 3 to 4 collectors experience,not just my own.As I have found this to be correct as well.

Here for a good time,not a long time.