This is the first of many items that came with my 1940 that really made the project worth purchasing. The pre-war chronometric speedometers differ from the post-war versions in the cable assembly. The pre-war version has a drive blade that sticks out the back of the speedo.
This speedo has the rev counter added to the face, which was called a revulator sometime after the war. If that marketing name was used before the war, I haven't seen it in any literature so far. This one is in very nice condition, and seems to work fine. Considering the date on the tag, I figure it is likely to be original to the bike. I'm not 100 percent sure, but I believe this was the standard speedo on the Tiger 100, optional on the Speed Twin.