Smilinjohn,
The holes to the left and right are,as you thought, for a spanner wrench to remove the bushing.The one underneath seems to be a socket head setscrew-curious.I would be interested in what Joe Steele thinks.
Mike
On closer examination, with better lighting and a bit of magnification, the lower holes appear to have roll-pins inserted, not set-screws, as you thought. Might, what appears as roll-pins, be inserted to prevent, inadvertant fallout of the bushing in the field?
Note: I understand that the Merkel 122 and Simson 76E (both top of line boxlocks) offered many options, not offered by some of the other Ernst Thalmann models; i.e., hinged-trigger; single selective trigger (even, with an additional set-trigger); bushed firing-pins; optional side-plate engraving patterns, in deep-relief; presentation Walnut, etc......and for really deep pockets, they offered the Luxus Grade. My 1985 Catalog (reproduction, not translated), even shows Merkel Model 8 Luxus.
