I'm looking to buy an Omega Speedmaster with a manual movement. And in doing my research, I know there are basically two available movements, the 321 and 861. But I also noticed there various case references and it seems they're not all worth the same.
In an effort to not overpay, can you list or rank the references according to which are most desirable/valuable?
It's a good question, because you're right, there are a few references and they aren't all worth the same.
As you might imagine, the older the reference, the more valuable. So, let's start right at the beginning (my estimates are just that, estimates, and assume the watch is in good condition or better with all original parts):
1. $55,000+ - Ref. 2915-1/-2/-3, c.321, straight lugs, lug width 19mm
2. $9,000-$20,000+ - Ref. 2998-1/-2/-3/-4/-5/-6/-61/-62, c.321, straight lugs, lug width 19mm
3. $8,000-$18,000 - Ref. 105.002 c.321, straight lugs, lug width 19mm
4. $6,500-$15,000 - Ref. 105.003 c.321, straight lugs, lug width 19mm
5. $5,500-$9,500 - Ref. 105.012 c.321 CB case, asymmetrical case, lug width 20mm
6. $5,500-$8,500 - Ref. 105.012 c.321 HF case, asymmetrical case, lug width 20mm
7. $4,500-$9,000 - Ref. 145.012 c.321, asymmetrical case, lug width 20mm
8. $4,000-$7,500 - Ref. 145.022-68/69 c.861 Transitional, asymmetrical case, lug width 20mm
9. $3,500 - $7,000 - Ref. 145.022-69 c.861, asymmetrical case, lug width 20mm
10. up to $3,500 - Ref. 145.022 c.861 1971 onward, asymmetrical case, lug width 20mm
That's the list which takes us up to the contemporary reference of the manual Speedmaster, 3570.50, which can also be had for up to $2,700 on the pre-owned market.
Of note, once Omega started to make a version with exposition case backs, they gave those watches their own reference. For example, the 3570.50 has the standard case back, while the 3572.50 has the exposition case back.
Personally, though, I'd prefer to buy a non-exposition case back Speedmaster, and get an after market exposition case back instead. You'll save hundreds, and you get to see the original movement as it was meant to be. Omega decorated the movements for the exposition case back models, and I just don't think they're as authentic or look as good.