I have an Ives with that same basic late motor, but with stamped wheels instead of the die-cast. The body appears to be a 5th series No. 1, but has that very late motor in it. Interesting to say the least. It appears to me that this motor has both Ives and AF characteristics at this point.
It never ceases to amaze and confuse me why companies like Ives and AF had such a plethora of body styles with minute differences in their cast iron locomotives. I would think that they would have made a couple of models, say a small locomotive and a larger locomotive, and stuck with those over the years. Perhaps a smaller version with a cheaper motor as a 3rd option for a loss-leader. Could it be that the wooden pattern got damaged or so worn out, that they just churned out a new one, and the differences can be chalked up to the style, taste and artistic interpretation of the current pattern maker? Or were the little details changed on purpose by the manufacturer for a reason? We may never know... but regardless, it sure does give us a lot of neat locomotives to collect!