Can anyone determine the movement in this speedmaster.
The watch ser # is in the 48350xxx range it is in the range that the movement could be a 861 or 1861 Just looking at all the gilt on the movement I am leaning to a cal 861 Sellers picture

 

Looks like an 861 to me, but I couldn't say with much confidence.

 

It's a terrible photo but it would appear to be an 863 or 1863.

 

Did they make a yellow (or copper) colored with 1863 in a display back?

Really hard to tell with the pics, but I would say its an 863.

 

Don't think so - this is likely an 863 since it has Côtes de Genève and it is gold plated rather than rhodium.

 

Good catch; I change my vote!

 

Thanks everyone for the reply This is the sellers picture the guy is local to me. However he is located at least an hour drive from me. This weekend I will try my best to meet up with the seller. I was hoping the caliber is the 863 I will hope for the best. I like these Speedmasters with the display backs. I have no Speedmasters with a display back. So this one is a good candidate to add to my collection

 

Could be cal.864 which Watchco used in some of their builds offered on Ebay a few years ago. Ive had one of these myself and, although somewhat unclear picture, i do see some resemblance -i THINK

 

Here is another sellers picture the watch appears to be well worn with a lot of scuffs on the bracelet. Easy enough to correct. If I purchase the watch I would just put a strap on her. I believe this is a 3572.50 with a cal 863 the serial numbers indicate the watch was built around the time Omega switched to the cal 1863 So I imagine the 3572.50 was produced with both movements. 863 and 1863