Thanks to all for your replies.
The scope I'm looking at has the original single vane secondary mount............problem NO.1
The Primary has a simple metal 9 point flotation mount with a fan in the centre and a ''strap'' that acts as a support(???) under the mirror?
The mirror clamps look very unusual and are suspiciously non conformative.
Trevor, 27 point flotation system????......wow!...........that 's beyond my expertise, but I'm sure that's why you get such great results.
The dob /truss construction seems o.k from the photos, but it's true rigidity is not known.
As in another thread I started on the Chinese 16 inch dobs around, I'm not very confident that the way to planetary heaven is through buying a mass produced large mirror.
I can see why many spend big dollars on large refractors
