I have seen “mystery numbers” on some vintage liquid thermometers. Frequently the number 12 or 13 sandwiched in between the actual temperature numbers.

I don’t know if the attachment uploaded, but if it did you can see the number 27 on the right side between the temperature numbers of 100 & 120.

Thanks for any input.

Beltrack [attachment]02ED025F-4F99-44B8-A05F-1E91224F08CA.png[/attachment]