It is a 12vdc to 114vac inverter to run electro luminescent dial kits......the Escos has one fitted as standard in the binacle to drive the dial illumination......You can however convert other cars to EL illumination by using an EL dial kit and one of these babies...

This could also be used as a replacement for your knackered Escos ones(And is well cheap...they are £26 in the UK)

HTH....