Hi Nick Well, they're the first images I've seen of a Dux. Brilliant!
Sorry, I can't help with the wood used.
Following convention used on many mowers the DX3 (Dux 3) is most likely a part number. Normally the sideframes would be numbered first (e.g., DX1 and DX2). Best guess.
The hooks are curious - maybe a sort of aerator attachment...? see attached 1963 example). Or a backlapping stand; or an optional different handle (from the single upright).
I have some bad news about that Dux advert. That's not a Scott Bonnar, but a Swedish side-wheel pushmower that sold here interwar and post WWII. [see ads below]
I have looked at SB newsprint advertising and have recorded about 3,000. For unexplained reasons, none advertise specifically the Dux or the Putting Green mower.
I have three thoughts about this: - [the effects of the Great Depression on sales] [the intervention of WWII killed the models prematurely]. [Scott Bonnar's desire to be the greatest maker of mowers in this hemisphere]
These are super-rare mowers, so sincere thanks for adding to the record.