here are BUNCHES of Zenith variants used for various "other" motors/vehicles in the pre-war (and post war) period.
I have a cast iron Zenith looking externally very much like a Tillotson "X" but marketed for Clark Fork Lifts.
I have at least three others each stamped with a different number but reading in period literature as "for Model A/B."
These "aftermarket" Zeniths typically have a round aluminum "stamp spot" riveted with one center rivet to which a Zenith number was applied somewhere on the top half.
It seems that the period particularly before WWII was a "competitive" time for carburetor makers including Tillotson, Marvel-Schiebler, Rayco, Mochi, and others.
Interesting video about half an hour.
https://www.youtube.com/watch?v=s1DpeS9yq4k
Joe K