The stepdown transformer you have there looks like a small arcade monitor isolation transformer, not normally good enough to run a pinball machine.

The serial numbers of the transformers are on the sides, can't see them from the angle of your photo.

From the pinrepair guides:

     8. Converting Gottlieb System 1 (1978-1980).

        Unfortunately these games are not easily converted from 220 volts to 110 volts. In order to do a voltage conversion, a pair of transformers need to be replaced. That's the two transformers (the small and large transformers) in the bottom cabinet. The small transformer outputs 3/5/11.5/14/69 volts AC. The large transformer outputs 6.3/8/25 volts AC.

            B-17921: small 100/115/130 volt transformer.
            C-17924: large 100/115/130 volt transformer.
            B-17923: small 220/240 volt transformer.
            C-17926: large 220/240 volt transformer.
            B-17922: small German 220/240 volt transformer.
            C-17925: large German 220/240 volt transformer.


The credit knocker is normally on the r/h side of the cabinet, just inside the coin door.