"X" means Non-Starter -- "-" means Abandoned
This may be why we cannot find any photos of the two "X" / non starter twin cams.
Official results here: www.tulpenrallye.nl/archive
Note 1: On 4 Feb 2017, Andrew Marsh wrote: "I saw your web page for Tulpen Rallye 1959 saying that my Great Uncle Mr F.A. Attwood was driving an MGA but he was actually driving a MG TF which he drove again the year after with his wife".