[Mgs] Electronic trigger

[Paul Hunt]

Anyone know what type of trigger this is?

http://www.mgb-stuff.org.uk/images/2007_12230058_copy.JPG

The black square is a power transistor marked BU941ZT but there are no other 
markings on the unit.  It came to me as a 'gift' from someone who got it 
inside a 45D4 distributor obtained from eBay.  He couldn't get the engine to 
run properly until he replaced it with points and condenser (!) and was all 
set to bin it until I said I'd like it to have a fiddle with.

Thanks
PaulH.