More for when your caravan is used at home I was thinking?
my thinking it's for caravanning?
Normally that type of enclosure is made for industrial use, to give 110 V ac from 240 volt mains, for operating low powerered power tools.
Now this looks like it is probably used as a 24 Volts ac supply for power tools, now caution, it is most likely ac, and if used to power a caravan will probably cause untold damage to anything connected to it, so don't be too hasty.
To be able to use it, you would need a bridge rectifier, and depending on the transformer,it may be possible to double up the output to give 20 amps.,
Caution, the winding outputs will need checking first before connection.
Also when the 12 Volts is rectified to DC, the peak voltage will be 1.4 times 12 volts, which is close to 17 Volts, whilst this could be used for battery charging, there would be no over charge protection, and if left for any time, could fry the battery.
If it was mine, I would have a look inside to see if there was a rectifier, then consider a rectifier, and voltage regulation to limit the voltage to 13.8 volts, but it would require quite a bit of re- work.
The rectifier and other components would be better placed in a well ventilated enclosure as there would be quite a bit of wasted heat.
BUT DON'T rush to connect it without checking the output.
Rustic