It is puzzling me also. I thought I bought a 74 case and was prepared to do the oil pump upgrade which now is already taken care of by the factory. The other side of the case shows 19/79. I had a look at a 70 2R case I have laying around, and that one has a similar stamp without what I think is the year.
A lot of cast parts have dates on them, I see them on cylinder heads, trailing arms and even on the chain box covers.
