Good evening, I just purchased this pusher on ebay, would anyone be able to comment as to its authenticity based on the seller pics? I need to replace this on my Cronostop and I'm wondering if I will need a gasket as well? Doesn't look like it comes with anything else. How would I be able to tell if it is aftermarket? The description is below. Thank you. NOS New OMEGA 086ST0015 086 0015 086-0011 Pusher 145.007 Chronostop