Some (all?) very late 65 Pan R-H cases have extra material in the casting.

It was in readiness for the oil line fitting that would be used for 66 Shovels. Therefore it makes sense that all 66 Shovels would have that extra material and they would have an oil line running from there as opposed to having an oil line from the centre like 65 Pans.

But in your photo I did not see that extra material and its absence indicated your picture was not of a 66 R-H case.
The R-H case in your photo could be 65 (early or mid) but Iím not sure and thatís one of the reasons I requested a photo of its BN. If not 65 then it may be 63 or 64 but there are a couple of things to check so, along with a photo of the BN, could you post photos of the rest of the R-H case please. One picture taken from the side and one taken from above. Thanks.

Re the gear cover, it may be 65 or it could be 66Ė69 and altered to operate like a 65? In the top of the cover is there a small hole just to the right of the oil passage bolt? Photo?