Escort MkII - when did it transition from round to square headlights?

Anybody know what year/month?  I'm referring to non-Ghia models here, as I gather they used square lights since the introduction of the MkII.  Incidentally, anybody know when was the MkII introduced exactly?
 
Thanks.

I have had half a dozen escorts of the last 2 years, and i have two 79 models, one with the round headlight and the blue oval badge, and one has a square head lights. then i also have a 80 model with the square head light front. so i would be guessing it would agree with flighter and say late 78 or in 79.

No. I had a 78 BC escort with round headlights. Also had a 75, 76, 77 and 79. Only the 79 GL had square headlights.

My 79 GL has round head lights.

Always thought it was the May 79 update that witnessed the conversion from round to square