Initially the spare wheel was secured by one of the 4 bolts in front of the "manhole" .... these are intended to receive the "hooks"(stored with the tank) needed to lift the turret and the identical arrangement can be found across the turret roof close to the gunners sight housing known commonly referred to as "Dog House or Garage".
The US ARMY introduced these newly seen "bracket" with the M1A2 SEP ... I first noticed them with the new arrivals in S. Korea a couple of years ago.
These were M1A2 SEPs already "prepped" with installments for the V2 upgrade which pursued about 1-1/2 years later.
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I actually have one of those in the making ... for quite some time:
The Australien M1s also sport this "bracket" now ... the M1s delivered to Marocco recently might have it as well ?
Haven't seen it it on USMC M1s yet.
Hope this helps.
Cheers
Christopher