This can be typical. The so called "square back alternators have better low speed performance. The "round back" were used with what you guys call "dual field" which is incorrect. "Isolated field" is the correct term. They were used up till 73? or so when the square backs came out
Below is the less desirable "round back." Notice this one is NOT an early that is 69 / earlier alternator. This alternator FACTORY had two field connections
http://www.forabodiesonly.com/mopar/attachment.php?attachmentid=1714557857&stc=1&d=1352052862
Below, on the right is the MORE desirable "square back." The one on the left is a ??? I don't know whether this was a factory little known edition, or an aftermarket case. Notice it has the early style GROUNDED brush at 9 o'clock, yet it has a position (EMPTY) for an isolated brush at 3 o'clock. THESE ALSO show up with simply a drilled hole from rebuilders and are a PROBLEM because they do not use standard brushes, are of usually low quality, and because the brushes can easily become grounded as well as a grounded brush accidently installed
http://www.440source.com/squareroundcomp.jpg
Below is an absolute POS This is a "rebuilders special." This is an early, 69 / earlier alternator which some rebuilder has drilled / hogged a hole in the case to install a 70 / later isolated brush. WHY THIS IS BAD. Because just like this one, the grounded brush is STILL THERE. And they don't use standard factory brushes, AND there's been numerous problems with the brush holders coming out of the box broken, missing hardware, and GROUNDED
http://www.hemmings.com/story_image/128306-500-0.jpg?rev=1
Just to be really clear, hear is an early 70's factory isolated field unit. These look just like the 69 / earlier, but had TWO field connections. The disadvantage to these is that they have low RPM charging deficiency. I'm not sure when the squareback came out, around 72 I think
