We had an earlier discussion on the “later” light switches on the XK 120, as specified in the DHC Spare Parts Catalog… For the article: see here:
I cannot proof that the DHC light switch was also used on other models (including my OTS) but it’s also not impossible.
Reading what John mentioned regarding the purchase of his light switch, there are many options as to what type it actually is. But as long as it does what it should do…