The only reason for the appearance of the word "speedometer" is that it is in the template for producing a dating certificate. I should know, since I was the person who created the template. In the case of a 1928 bike, the "speedometer" heading is redundant because the column in the Despatch Books labelled "Speedometer" or "Speedo" did not appear till after WWII. Before WWII, if a bike was fitted with a speedo it would appear in the "Remarks" column. The "Remarks" column for your bike reads "Twist grp, Leckie Sad".
As I have advised the current Machine Registrar, one should never underestimate the ability of Ariel Owners to misinterpret what you provide them with in terms of Dating Certificates or instructions upon how to obtain a registration number.
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.