Getting close to a source for f85r2

[ReneZ]

I wonder what the odds are of an earlier Regimen still being out there. 
Virtually impossible?

I do not know for a fact, but the appearance strongly indicates to me that the 'Hanschriftencensus':
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is well maintained and based on all known scholarship related to German medieval manuscripts.

So what are the chances? I think slim, but there are still private collections without public catalogues.
From time to time, famous manuscripts in private collections are known and have been described in some detail,
but this is certainly rare.
I can't remember ever having seen a MS in a private collection being referred to in the Handschriftencensus.