There was a fairly big discussion of the "ways, means and ends" of the whole "seconds" thing with Caithness, just recently.
I believe is is suspected that some bits were even marked as seconds just to shift them quickly at the shop-end of Caithness - they were also remarkably fussy - it can be very hard to find any minor flaw in many official "seconds" too.
It could even be a way of getting around the "limited edition" numbers.......
I think your things are wonderful, and definitely Sarah Peterson.
Currently, I believe she is a major "tour-de-force" - almost keeping Caithness alive single-handedly (according to a major fan of hers, the engraver Bruce Walker, with whom I had a lovely discussion during the summer.)
Given the differences between yours and the "final production" model, I think "prototype" is likely to be accurate. Bruce told me that she works very hard to ensure that all her designs can be made to production standards by all the makers
who are currently in action.
Perhaps yours are one she made, but when it came to production, the other makers couldn't quite manage her standard in the allocated time they have to produce each one, so the design had to be made smaller and simpler?