Franken watch?!?

Dear watch experts,

I have recently purchased an Omega Constellations which i have always been on a lookout. When i finally stumbled upon this nice looking Constellation, it didnt took long for me to do an impulse purchase.
Call me an idiot, but i only started doing research after i paid for the watch.
With my limited resources, one thing i concluded is that there is a very high chance that this is a franken watch.
Can any experts here tell me what model i am having? Coz i have exhaust all available info i could find but still nothing similar pop out.
I thought i got a cal.505 movement, but further checking shows that the rotor doesnt look like it belongs to a 505, more like a cal.503 if u asked me.
Pls help. Hopefully these attached photos are helpful. Thx in advance.

It could still be a 505 movement with the wrong rotor from 501/503. But, this case reference 2493 should come with the 504 movement which has a calendar. Along with the bad redial, this franken is not something worthy to keep.

Hi, thx for the comments. I did go to Omega's website and keyed this ref, the photo of the watch that relates to the ref has a diff dial.
I guess the only upside from this purchase is that i got it cheap. At least to my own opinion.