[Healeys] BN1 100/4 Drain plug size and thread

[STEPHEN CUSS]

Hi I asked this question a few weeks ago but only got a partial answer, can
anyone help me with the size of the plug and the thread type, as i am trying
to order a magnatic drain plug for my BN1 and need to know the thread type and
size, the car is original with original sump.
 
Thanks in advance for your
help with this matter
 
Steve