Got this old Szim lathe I'm working with at a new shop and in trying to identify what style of spindle nose this is. It looks like a typical short taper except the threaded holes are on the chuck/adapter plate instead of on the spindle nose. Haven't seen this style before and I'd like to have a name that will let me look for more adapter plates/chucks designed for this spindle nose.

Looks like a type A2-8 short taper except the holes on the spindle nose aren't tapped. It's got this weird slotted bolt hole pattern on the back that rotates into place to secure the bolt heads while the bolts actually thread into the back of the chuck or adapter plate.

Thanks in advance.