Old AF 1250 Transformer

The top plate has the terminal combinations for various voltage combinations. Posts 1+2 give 5 1/2 to 8 volts, posts 1+3 give 8 1/2 to 11 volts, posts 1+4 give 11 1/2 to 14 volts. You can try the 1+3 combination, but that may be too slow, so then use the 1+4 combination. It would be recommended to change the AC cord to one with a molded plug on the end, available from any train parts supply house.

Larry

Using a circuit breaker on the track power would be a good idea. I don't think one was built into most them back then. It could save the transformer in a derailment. Vintage breaker assemblies as a separate item were made, but a modern automatic-resetting automotive breaker are better, and could be hidden, or maybe added as an internal transformer mod. Maybe hide anything "modern" in an empty transformer case, or similar. Match track breaker to your transformers watt/amp rating.(a power strip with a breaker for the transformer would be a good idea too, with the old cord.)

While your transformer may still work as designed, I have a personal dislike for old, metal cased transformers. I just don't think they are that safe. I was just inside a Lionel 1042 transformer because it needed a new cord. The solder terminals for the 110 volt cord were only seperated from the metal transformer supports by a piece of thick fish paper. Both the supports and the terminals were touching the fish paper) The control wiper arm came uncomfortably close to those terminals too.  After seeing these things, I decided not to replace the cord. The transformer will be a shelf piece.

I'd suggest getting something newer to run your trains.