Datejust advice please

[bonsai-man]

Advice needed please, looking to buy this watch. Seems reasonably priced at £1400 with no box and papers. Can anyone tell from the picture if it has the sapphire crystal and if the bracelet looks right. It has lug holes so would be about 1979 - 1986. I asked the seller for S/N but as it has no paperwork they could not say. I have only seen the newer bracelet.

Also I have large wrists the watch has 20 full links, I think these come with 22. Does anyone know how long a new unadjusted bracelet would be. I think if I divide the length by the number of links then multiply by 20 I will get a good idea of the size.