Sugino RDs - driving me nuts

I’ve got two sets of Sugino RDs, a 170mm set and a 165mm set.
The shorter set were bought more recently and give me a 45mm chainline as per Bens Cycles description and a few other places.
The older set give me a 42mm (and silent) chainline - perfect.
Does anyone know how to tell the difference between these two crank arm sets?

I think you’ve answered your own question?

Where are you in adel? I have a printed copy of this that you need to examine.

In the city during the week. Polo on Sunday.
Printed copy of what?
Are there stampings on the arms that tell me the difference between releases?

Not really. The two different chainsets give me different CLs on the same, genuine Sugino 103mm JIS BB.
It looks like Sugino changed the arm design and never bothered to tell anyone but I can’t find anything definite on this.
There are ppls in the London Fixed forum that are running the ring on the inside with a Shi-tmano 107mm BB and it gives a perfect 42mm.
So what’s up? Did Sugino change the offset of the drive side when they changed the lettering on the arms?

It doesn’t look like anything stamped into the arms tells me when they were manufactured but I haven’t pulled both sets to compare.