Unfortunately no part number... just a bunch or really fine coils... I tried to be careful but I cut through them.... Perhaps I'll buy another unit so I can find out how many coils etc... but I guess we have an answer. I am not familiar with transformers. Logic tells me this one has a comon ground...input is boosted drive the piezo at higher voltage... I did a very brief search of farnell but didn't find anything similar... Anyone know part numbers or supliers of small 3 pin tranformers?