Thanks for the additional confirmation.
I am guessing all the additional comments and humor are implying a duh! moment?
Yes. We tend to get a bit silly at times.
And yes, the entire range of Esterbrook nib units fit on any model from the Dollar pens through the Safari models. There *have* been discussions about whether the larger size 9xxx nibs look oversized on the small SJ models, but I found one "in the wild" last summer with a 9128 (flexible extra fine) nib on it, at an antiques mall about an hour from where I live.
When I first found my way here, about four years ago, some people were still treating Esties as 3rd tier brand pens. I thought (and still think) they're wrong. Especially after acquiring some *real* 3rd tiers (a few Arnolds and a Wearever -- although the Wearever writes well enough, and was free). But there are a lot of others who recognize Esties for being good pens, where all the R&D went into the nibs.
Ruth Morrisson aka inkstainedruth
"It's very nice, but frankly, when I signed that list for a P-51, what I had in mind was a fountain pen."