Cylinder date codes?

[wareaglescott]

Car is a 79SC
No records so I always like to find little clues about what might have been done in the past.

Noticed today the following date codes on my cylinder heads.
1 of 4/78
2 of 5/78
3 of 6/78 (these 3 are all on the same side)

Anyone have an idea if that is normal or might indicate they have been changed at some point? I am thinking probably original but wasn't sure if there was any significance to a 3 month spread.

Thanks

[Flat6pac]

I would go with production arrival. Possibly more than one vendor product arriving at different required times.
This is seen all the time on a single engine.
Bruce