Early 20's Citroen 5HP. ?  (  https://www.citroen-5hp.org/utilities/formhelp.php?category=register&lang=EN&help=vergaser ).              All threads are good , float is sound , very little discernible wear on the spindle , no light past butterfly . Float is marked 33GR , TOP and E , Float valve 2.0 ,  26-16 on venturi and 70  (I think) on mixture . Bore is 1" and fixing hole c/cs are 1- 7/8" .  Be interesting to know if this is specific to Citroen or whether  (as someone suggested)  they were also used on stationary engines of the period .