Stephen,
I'm not sure what to say about the data plate. The original fasteners would have been rivets, not screws. Interesting that someone felt the need to remove the plate.
My information is somewhat limited, but what I can say is -
if this were a 1963 model, it would have been a J404X (no P7 feature),
if this were a 1964 model, it would have been a J446Y (no P7 feature),
if this were a 1965 model, it would have been a J446 (no P7 feature).
The above numbers are for GE's best 40" freestanding range with one oven and 3 storage drawers.
My 1966 catalog doesn't illustrate any 40" ranges, apparently they had fallen from favor sufficiently to justify not including them in the catalog (although they certainly were offered). It also appears that 1966 was the first year that GE offered the P7 oven in a 40" range. The black trim across the oven door and left storage drawer is a rare trim element, possibly offered for one year only. John (Combo52) has one of these in Coppertone, I seem to remember. He might be able to tell you more about this specific model.
It's beautiful, I hope you can use it and that you find it to be, for the most part, fully functional.
lawrence