Introduction of Sapphire Crystal to Moonwatch

Hi,

Can't seen to find an answer to this, but probably not looking in the right place. Does anyone know when the option of a Sapphire Crystal was introduced as an alternative to Hesalite on the Moonwatch. I'm assuming it was the same time as the display casebacks of the early 90's.

I ask because I am looking at a (declared 1984/1985) Speedmaster with solid back that looks like it has a Sapphire crystal. However, the type of damage would be consistent with Hesalite.

Have only this photo and no feedback from vendor at present. Thanks in advance.

Hello Socks,
The first display back is really older, it was the 345.0808, in 1985, and the glass was hesalite. And I looove this ref.... 😜
The first sapphire glass appeared around 2002 (ref 3573.50 or 3572.50), with display back... so called the "sapphire sandwich"...

For info... I'm not an expert!... (I just have MWO edition 3... 😉 )
So, if I made some mistakes, be sure "real" experts here will fix that...!

B.

Oh exact...! the limited "Jubilee" was the first... 10 years before...!

Thanks for that all!