Where did you get it, and what are you proposing to use it for?
What do you mean by a "Dimmer transformer?" It is not for a neon. It is only 12v - 24v input and output. It does appear to be meant to be mounted inside a housing.
In the main neons are AC, and a neon sign can be a very high voltage, the device you show is DC looks like a step up inverter 12 to 24 volt and does not seem to have any control, so can't see how it would ever control a neon sign, so it seems you likely have described it wrong or have wrong device.