The belts in the listing seem to be of 1970 style.  The lift to unfasten lever instead of the push-button.  Therefore it must be a 1970 model.  The seat belt latch tells the story.  Undeniable!

Thanks, that confirms my memory. Mine were the lift type.

The lap belts on my 72, 11/71 production date, HLS3056539.

The lap belts on my 70, 6/70 production date, HLS3005957.

The belts on my 71, 8/71 production date, HLS3041924.

Found another 12/70 build "71" with 70 belts.  What's it all mean?!  

https://bringatrailer.com/listing/1971-datsun-240z-218/

 I'm beginning to think they changed belts mid year in 71 along with a number of other things. 

18 minutes ago, Zed Head said:

Found another 12/70 build "71" with 70 belts.  What's it all mean?!  

https://bringatrailer.com/listing/1971-datsun-240z-218/

Using up existing stock before moving to the updated parts.

Have the same in mine (build 12/70).

Racer X is right on the money. Lot of time spent trying to "solve the mystery" when it's just simply a matter of small production anomalies. I see this kind of stuff in my shop ALL THE TIME. Hear about it from my parts customers ALL THE TIME.  

So, @zspert is a 12/70 build date a 1970 model or a 1971 model?  What is the difference between a 70 and a 71?  That's the question.

When I was a young Datsun dealer mechanic, no, not a Tech, a mechanic, way back in the early 70s I was sent to several factory training schools -  mostly in NJ - where we were taught that a 12/70 240 would be a 71. Of course there are early 71s and late 71s but that's another topic and Colbert is coming on soon so I have to go.     Cheers