Hi Chris, I have done some research on the Ransome cutter unit, and it still appears to be in production on the Masport/Morrison Olympic models 400-500-660. It is not a sealed unit....the rivets on the knife-blade can be removed and are listed as a spare part....the bearings can be replaced also.
Here is an exploded diagram of the unit disassembled....
[Linked Image]
Hoping this helps,
cheers2

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Kindest Regards, Darryl grin