Hi,
I`m just curious and any comment/info is welcomed.
I have few of this watches and I have noticed slight differences in the Omega symbol in the centre.
NOV1966 big triangle is having smal rounded logo, similar to current service crystal, but thin font, flat feet.
Very hard material, more difficult to polish than any other hesalites i have experienced. Inner cracks.

MAR1967 no triangle tall, narrow, very thin font, flat feet logo.

Both of course HF case, flat1 bezels.

If anybody can tell, if the crystals are correct for the year, or any info based on your watches/experince is welcomed.
Last pic is my watchco contemporary crystal for comparison. Thank you.

 

I see these differences on Constellations as well, it's a good reminder to add the crystal type as a data point too in documentation efforts