I would link you to the thread John (JPS) illustrated his rifle, it was on gunboards during 2006 which means it was purged, so all I have are the pictures and the text that I saved. The pictures are pretty poor though and not mine to post, but his rifle was a Amberg/1890 3025/e; the Storz rifles are Steyr's, one 1890 (page 159-162), generally a good description, but more a historical outline rather than a detailed examination. I also have a record of Craig Brown owning one, Amberg/1890 7622 l, but very few details regarding it.
I did notice on the Storz examples (museum examples he had access too) the letter marks Storz refers to on page 162 as related to the conversion is on the left receiver (serial side), whereas John's example is on the right receiver (all different letters); John's rifle also has the "circle W" (Will Company) next to the trigger guard like Storz's examples.
Anyway, I guess that makes three examples known, two in Storz book, John's and Craig Brown's. Not sure what happened to CB's example, supposedly it was matching, but that would actually make 4 known.