Hmm cant find any data still, I think pulling the lid off and looking in is the favorite.
Also I think the module is incomplete as references to it on the web show it with a base (socket and bracket) which includes another board part of the base, this is not included, I suspect this board will be the temp controller, as the seller shows the unit croc clipped up and showing 5mc's on a freq counter, so the osc circuit must be built in to the module, so the seperate board on the socket bracket is either temp control or perhaps a buffer amp, hopefully the latter.
I did find a pdf that shows rudimentary info, the /5 means 5v supply.
I might have to use a pic and a ds18b20 to control the heater, thought that entails a load of testing that I wanted to avoid.