11 of it's datasheet Rev C.
This is a funky application where they use the Vos pins to unbalance the front
end and then provide feedback on the other Vos pin.
The OP90( released 1986) has been around for a long number of years, so I would
be inclined use a more recent InAmp device instead, such as the AD8237, AD8235,
or AD8236. Or alternatively roll your own with two or three op amps depending
on gain/bandwidth/supply current needed.