Those are precise machinist levels used for setting up machinery.
Is the Stanley 36 series level a machinist level? Stanley was rather vague in its catalog about the rating for the levels, and I always assumed they were high-grade carpenter's levels, since Stanley offered a series (34 series) of levels similar to the pictured Starrett level.
In the 1958 Stanley catalog the "34v" is listed as a machinist level and is nickel plated. And yes it is similar in shape
as the Starrett "98-8 in the Pic from coolford.
The "36" (smooth bottom) and the "36g" (grooved bottom) is listed as a Japanned iron plumbs and levels.
Recommended for carpenters, plumbers, millwrights, electricians, etc. And the "37g" is the same as the"36g"
but it is nickel plated.
One difference I see other than the shape is the "34" series uses "ground glass" and all the other levels use "proved glass" vials.
I have a 24 inch "36g" and one thing I know is, it is not very practical to use for finish carpentry or plumbing and I have
done both in high end construction.