What Happens When a Copper Wired Component is Introduced into an Antique Lamp with Aluminum Wiring?
I doubt it was aluminum wiring , in fact silver or tinned copper is more likely for fixture wire , butt connectors would work ok for either of the 2. If aluminum corrosion may have already started. I would check for signs of thermal stress at the connectors. I actually have run into silver several times because silver was available at times when copper was not but including solid silver buss bars . I have never seen aluminum fixture wire.
Note tinned copper looks just like aluminum but aluminum is brittle and just a bend or 2 it starts cracking and breaks. But I doubt it is aluminum.