http://www.dentrinityshop.com/photo/OTA_S/tnsig002.jpg
Comparing this image to my ICS pin, it appears that the position of the two nubs that prevent it from moving are in a different place between the Marui and the ICS. The ICS nubs are right at the bottom, whereas Marui's pins look like they're only 3/4 of the way down the pin.