[papajam]

Just a bit of an FYI on the following;

I do suspect that it was either spinning at engine speed for a while...

Technically, this can not happen because of the sprag clutch in the starter drive. This sprag clutch is a one way clutch that is engaged when driving the flywheel but is disengaged if being driven by the flywheel. This is to prevent the armature in the starter from spinning too fast and flying apart (like if the engine starts and the key is not released right away).

 

[papajam]

Not an expert in this area by any means but my understanding is that the 130 tooth flywheels need a starter from a 72-74 2l or from a Series 4 Spider.
Since not all later Alfa parts manuals list the Bosch part number, trying to cross reference Bosch part numbers is a feat worthy of applause. Not to mention that an original OE fitted starter from the factory may not have the same Bosch number that's the book.
Bottom line is that I think that the 1005 821 071 is NOT correct for your flywheel.

 

[papajam]

Just an observation here to add to the confusion. Note for example the 1005 824 071 number is on the nose housing. Alfa and Bosch have typically used the number on the field coil housing as the starter assembly number. The Series 3 Spider starter I have here shows 1 005 231 071 on the nose housing but the complete starter is listed in the Alfa parts book as 0 001 108 024, the same number that's on the coil housing. It would seem that the 1005 824 071 is the part number for the nose housing only.