Momentary disclaimer: Notably, this Thread initiated concerning PRE '64 exclusively, and my above Post in that context only. Post 64 Mannlicher Model 70 rifles Factory catalog infor included below.
Re O/P & subsequent Web link provided... Woah Bro!!! NO seller tassertion hat Pre '64 is any sort of "factory original"!!!
The condition would account for the "as is" sale. But too, such regarding any actual assertion of originality as in NOT. More than a leap of faith reading in some sort of rare factory variant. Excuse me "160user", but whatever those "160ies" are, maybe better stop "using"! At least perhaps when operating machinery or contemplating such as your post here.
Would have saved time/effort had you just provided the listing OR narrative up front! More than enough wild claims associated particularly with Internet sales, the exemplar here, no such inference of "originality"!!! Appears an honest seller & wishing him/her well!
As to the "how arriving at such condition...?" Agreeing sad, but causation; personally, "so what"?
The other 'stuff' concerning John Olin & Model 54 factory Mannlicher... 'Perhaps true', but I'm with others here suggesting PROVENANCE! Jack O'Connor was a great gun writer with established reputation, but integral with his occupation; selling copy! Other eras, just to report, not question sources. Perhaps rule here... Buy the copy, not the story!
AMENDING my moments earlier words. Post '64 era Mannlichers listed in my source pdf Winchester Catalogs years: '70, '71 & '72; '73 not. ('68 & '69 catalogs pdf unavailable). Illustrations Mannlicher displayed without sights. Narrative specs including: $259. 19" barrel, European styling (w/Monte Carlo stock, not in my book) "detachable" barrel sights (presumably secured with screws), chamberings in 243, 270, 308 & '06.
My take and...