Hi
I think from memory the difference between the -35 and the -40 was the -40 had extra internal wing stiffening ?
So I think it is quite feasable, that if the new modified parts were not yet available for fitting that aircraft on the production line, aircraft ordered as -40 were built as -35, until parts were available, enabling production output to continue.
So presumably the contract would show a -40, but the manufacturers plate & aircraft card would show a -35.
Then again,for example on some Ju-88 A-5's, had Ju-88A-1 data plates.
cheers
Jerry
a good serial site
http://www.joebaugher.com/