I've not seen that before.
Seems you have a stainless bushing (bague d'usure) with threaded holes in the face...ours have always been bronze with no threaded holes, but always easy to remove. The bronze ones do wear hence the name bague d'usure (wearing ring).
Was there any noticeable wear on the stainless bushing you took out?
I wonder if stainless is standard for A55s and bronze is still standard for our older Amels?
I need to order a kit, it will be interesting to see what turns up.