Red white circle 9 / 6 number sign vintage round metal plate

Soviet retro round number sign 9 or 6.
I can’t say exactly where this type of number was used. It doesn’t look like it was the address number plate of the apartment. Most likely it is possible as the number of a bicycle or maybe a go-kart, pedal car.

Original vintage number plate. 

Made of enamel metal.
Diameter is 67 mm.
Weight is about 30 g.