1967 OMEGA Constellation 168.017 Cal.564 (565)

I purchased this watch in the mid 80s. It looked and ran well at the time. I vaguely remember having it cleaned. It appears, however, that the movement (or parts of it) had been replaced. The minor amount of research I have done thus far has shown me that the 565 caliber is not an adjusted chronometer movement as is the 564 which should be in the case. The photo of my Constellation case shows the model as being 168.017. A 1967 stainless steel "C" Constellation. (Adding to my confusion is that there are 2 separate listings 1967: "C" ST 168.0017 Caliber 561/564 and "C" ST 168.0009 =168.0017 Caliber 561.)
To my point and question: The 565 seems to be an inferior movement to the 564. It was used in Omegas 1968 Seasmaster and Geneve. In any case inferior or not it is not “original” to the watch.
Making this discovery after 40+ years is disappointing. I do not believe I would have given it to a local jeweler or watch repairer. Although they would have acted as agent to forward the work to Omega. I have found no paper work confirming that Omega did the cleaning. Is this something that Omega service would have done? That is swap out a movement without notifying the owner. To what degree is the intrinsic value of this watch diminished? Should I invest in returning an original 564 to this watch if one can be found? Finally, what would the approximate cost of restoring it be it that is even possible? Thank you in advance for any helpful replies.

Welcome @SteveGuitarist

You are correct in noting your watch has the wrong movement.
Omega is unlikely to have done this, more likely a local watchmaker under the instructions of a previous owner.

If you could post clear close up pics of the watch (front sides back) you may get better advice on whether it is worth spending money on restoring the watch to its original specs.

Like 5% of watches I buy that should have a chrono numbered movement has a 565, so it's very common, and 50+ years later, the only difference is "correctness" - no physical inferiority if you ask me, maybe even superiority as it's more likely that 565 has revisioned/patched parts

It does make the watch unappealing to a collector though, price difference is 20% ish at most in my opinion

I experienced what happened in 1980 myself once too, brought a 564 for service and dropped a 751 along with it, the bottom parts are same, when I received the watch it had a 751 movement installed ... after that experience I picked up watch repair myself

My primary concern is the condition of the watch - hence asking for more images.

If it's pristine with box and papers, it might be worth spending money on.

However, from the pics we have:
there appears to be a substantial mark on the dial between 11 and 12.
the crystal has a cyclops which may or may not be an Omega crystal.
the case looks okay but it's impossible to tell the condition of facets/brushing.

If the watch is just a nice daily wearer, I would leave it as it is and wear it - as others have said, the 565 is a very good movt, just not chronometer rated (although, if it matters and if the movt is in good nick, a skilled watchmaker could regulate it to get damned close to chronometer specs)

My advice is to do what gives you pleasure. If having a chronometer movement in your constellation works for you, by all means do it. I know it would matter for me.

These are mass produced objects and parts get replaced all the time, so swapping the excellent 565 for an excellent 564 (or 561) is no big deal. Its like a Porsche 356 with non-matching numbers, it may not be the engine it left the factory with, but it's still a 356.

Wow! First let me say I am overwhelmed by the generous responses. Pardon the delay in expressing my gratitude I not been able to check the forum before today. I won’t be able to post other photos for a day or two. I will say that the watch face is not pristine by any means. Condition aside, I have been convinced by a few of your posts stating that the 565 is not necessarily an inferior movement. The “quick change” aspect makes up for the correctness of the watch. And, as it has been remarked, putting in another 561 or 564 would still not make the watch original. The box and strap, by the way, are of course not original. I tried to do the watch justice by dressing it up right.
Just as a point of information. The original owner was my tailor. Mr. Rosen, a survivor of the Holocaust, asked me if I wanted to take the Omega off his hands for $250. It was around 1985. I had no idea how much this watch would be worth to me back when I was 25. Frankly, it’s the main reason I was upset about it being bastardized. Off topic my mom recently passed and left me my dads Omega. It’s a 1952 14k Automatic (G6525-Cal.354). It runs spot on. But, it needs a new crystal and probably a cleaning. I need a reputable watch repairer in Queens, NYC. New thread I guess.
I’ll post better pics of the Constellation (and the G6525) as soon as I’m able. Again, thank you all.