John Riggs wrote:
The initial take down in aikikai dojos can be very similar looking between ikkyo omote and nikyo omote depending on the attack (especially a grab). The pin will distinquish the two.
Compare Best Aikido
pp. 110-111 (ikkyo omote executed from katate dori, with kote mawashi, but without the nikkyo lock, which makes it ikkyo) and pp. 130-131 (nikkyo omote executed from the same attack, now with the lock, which makes it nikkyo).