OK Rob, good pickup - I hadn’t noticed.
The p.20 Front Axle and Brake illustration in the 1938-9-40 post-war issue, reproduction Handbooks is totally different from the p.20 illustration in the 1938, 1938-9 and 1940 SS Cars issue original Handbooks.
The post-war illustration is as previously shown with as you say the ‘piston type Luvax’ front shock.
The pre-war illustration shows the distinctively different apperance ‘vane-type Luvax’, with filler plug clearly on top. But again - its still same picture in all three pre-war Handbooks, with no revision. And apart from the shock, there are a lot of other detailed changes to many other components shown in this photo - totally different car (Maybe the 1.10.48 issue 1938-9-40 Handbook is using the 1946 (Mark IV) illustration - I could check, but not really of relevance)
Now this page 20 illustration supports the section on BRAKES.
Interestingly page 39 is the section that talks about the Luvax Shock Absorbers, including a photo of the ‘vane-type’ Luvax shock, and this whole page text and photo is the same in all three pre-war SS Cars handbooks, and indeed remains unchanged in the postwar 1.10.48 issue 1938-9-40 handbook. This postwar handbook is meant to be a replacement handbook for all 1938, 1939 and 1940MY SS Jaguar, so seems they have simplified description of shocks rather than cover both vane-type and piston-type. Bit naughty as p.39 talks about refilling oil and adjusting the setting of vane-type shocks (by turning the regulator screw), which may or may not be applicable to piston-type. Don’t know.
Just to check - the 1937 2-1/2 litre Handbook has different again photos for page 20 and 39, but still shows what looks to be a vane-type Luvax shock, but different enough in detail to be a different model?
With the 1-1/2 litre Handbooks, as before the Luvax shock detail has been updated - the 1939 handbook details/illustrates the piston-type shock, and the 1940 handbook totally rewrites, referring to piston type but no illustration