I suspect they are different, I was sold a Cabby one from ebay being told it was from a Coupe.
The housings and back plates are swappable though.
This is cut n pasted from my post on the RCOC when I swapped mine over :
Remove the mirror from the housing, there's a small spring clip just visible along the top edge towards the outside, slide this outwards and the mirror and backing should come away, disconnect the heating elements.
Leaves this :
These's 3 small clips that hold the motor into the housing, these need to be removed, gently prise them off with a small screwdriver or pliers, I found a squirt of WD40 helped, try not to loose them.
Remove the spring that is hooked over the clip in the back of the mirror, this can be quite strong. The 3 clips that hold the motor to the case are visible on the LHS.
Everything should be quite loose now
Now you need to remove the 5 wires that control the mirror from the plug to allow everything to come apart.
These are just a push fit, held with a spring clip. Make a note of where each wire goes in the plug.
Looking at the plug end on, insert a paperclip (or similar) just above each pin and push, the wire should withdraw quite easily from the back of the plug, if it doesn't try again.
Once all 5 wires are free, the whole lot should come apart.
It looks as if phase 1 and 2 mirror internals are the same. I wanted to fit the mirror from a Cabby to my Coupe and used a later model of Coupe mirror to supply the mounting (thanks Jinxy).
As all the best manuals say, reassembly is just a case of reversing the procedure.