hi,
Its a Transformer Blocking oscillator.
I have drawn the windings on this image, excuse the poor quality of the windings...
Looking at your images, it shows the transistor legs bent to a 0.2inch pitch.???
Are the base pins of the transformer also inserted on 0.2inch pitch.??
If yes it looks as though you have the transistor inserted incorrectly.??
By using a 12V transformer instead of a 6V transformer it may not be providing sufficient base feedback to cause oscillation.
E.