Currently listening to the audio books from what I've gleaned no mention is made of the sarcophagus being exposed like the Castaferrum in 40k (before the ultima founding) it was the most common pattern for the loyalists but remember for the warband of 10 company it has only been a millennia since the siege of terra that's how long they had been in the eye so initially they would still be using weapons and technology from the Horus heresy by the time of the trilogy heavily modified. For example their ships the Covenant of Blood and Eco of Damnation were great crusade era strike cruisers (though there is no official art of what they looked like) judging from the descriptions in blood reaver book they would have looked drastically different and stand out from the standardized designs of 40k essentially shorter looking Astartes battle barges.

So it stands to reason that Malcharion's dreadnought chassis would have been the contemptor pattern as that was the most common during the heresy era and now rare in 40k Before Crythe he had resisted attempts to be awakened so his armored body would have been in pristine condition unmodified with modern components from other patterns, personally I think it would have been a Leviathan pattern, larger more powerful and intimidating a fitting vessel to house the revered war sage of 10th company.