G'day all
Yep, the Regal was Rover's top-of-the-line domestic lawnmower.

The 2711 certainly had a 11 Series Briggs - but not the I/C specification.
Note the up-market air cleaner cover and muffler guard used on the I/C version.

The 2711 is shown in this brochure:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=67345

Cheers
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Jack