Hoping you find a box quickly for the suffolk, My vote is for the number 2 machine as it will be the most dramatic turn around of the three, Thanks for posting the vids.

The early cast iron Punches did no have Mk numbers but Series numbers which , as far as I can ascertain, were not displayed on the machines , but only appeared in the parts books. As your machine has a freewheel on the rear roller rather than a dog clutch it will be either a Series 1 / 1a (1954/55 ) or a Series 2 (1956). The 1957 Series 3 and onwards had the rear roller dog clutch. Interestingly there is a note in the pars book page for the Series 2 that states it’s fitted with a moveable intermediate sprocket spindle to adjust the tension on the intermediate and final drive chains. So if Richard’s machine has a moveable intermediate sprocket , it is a Series 2; if not a 1 or 1a.

They all deserve restoring for several reasons but in my opinion it's the Dronsfield as its a rather unusual machine also it's complete.

The Ivanhoe, looks like to Rolls Royce of mowers, think it needs to be the next. Or weld two together Alan Millard style. 😁

My initial reaction was to say the Shanks. Of the three major early manufacturers they are probably the least well represented. However on reflection it has to be the DB Swallow in terms of presentation and preservation.