Jamesmac, the short answer to your question is the S880 configuration was used as an Elimona for a while. Yanagisawa is known for making running improvements within model runs, but overall, their model changes are not as confusing as people make it seem.
Here is the long answer, which specifically pertains to straight sopranos. The timing for curvies is a little different.
When the Elimona designation was introduced, Yanagisawa only made the S800 as their soprano offering, although in some markets the S800 was designated as 2100SS toward the end of this model run. This model is frequently compared to the Selmer Mark VI with bell and palm key tone holes on the front of the sax.
The S880 introduced replaceable necks and a complete change in tone hole arrangement with bell and palm key tone holes shifted to the left side. This allowed for better ergonomics including a true pinky table. As far as I have been able to ascertain, all S880 models (aka 2200ss in some markets) at this time received the Elimona designation as flagship of the line. Yanagisawa prudently continued to manufacture the S800 as their integrated neck model for those who preferred that successful model.
In about 1990, Yanagisawa introduced the S900 as their integrated neck model. Tone hole arrangement was changed to match the now successful Elimona, but additional changes were also made to the key work mechanics. The most readily visible change is the arm that assists in holding the C# pad cup closed. Previously, the arm had originated on the C key pad cup. On the S900, the arm extends from the rod to the C# pad cup. Similar changes were made to the S880-Elimona key work.
In 1992, Yanagisawa officially introduced the S990 as the first soprano model to have a high G key. Afterwards, only S990 received the Elimona label as the new flagship model. Yanagisawa again prudently continued to market a removable neck model keyed only to F#, labeled as S880 as well as the integrated neck S900.
Yanagisawa’s next major model change kept the same key work, but modified the bore of the body tube and the placement of the tone holes on all models to improve intonation, etc. The S990 became S991; S880 became S981 and S900 became S901. This account, of course, ignores models of bronze and silver and custom work.
So, the body tube of your S880 is ostensibly the same as the original S880-Elimona, however you have improvements in the mechanics of the key work. And just as a side note, my favorite classical soprano saxophonist, Remko Jak of the Amstel Quartet, plays an S880. It is beautiful.