I think the type certificate of the type (R1/ R2/ Clp 1/ Clp 2/ etc) would define the aircraft for ever.
The R2 has a different engine and slightly different parts for the tail rotor etc.
An Astro remains an Astro even if upgraded with oil filter kit, hydraulics kit, 10 hole panel, etc
I sense R44 sales in the UK have slowed of late - from new registrations each month