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Is there a market for them or are they worth bullion value only?
It's really a matter of supply and demand. Spence has indicated that he located multiple sets via internet searches, if multiple of the set are readily available for easy, low-cost purchase it would seem to indicate that supply exceeds the demand from collectors of Apollo 11 material. It would be among such collectors that you have the best chance of selling at a premium over melt. Coin collectors tend to "look down" at medals and consider them of little value beyond melt - their loss IMO.
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And would you recommend leaving them as they are, dipping them or cleaning with acetone?
Based on the images (vs. in-hand inspection) it would appear that acetone would do little if your goal was/is to remove the heavy toning. If such is the aim, a dip in a product such as Jeweluster (or its equivalent in the UK) might do the trick.
If you go that direction, I would begin with a solution that uses a 50/50 dilution of the acid with distilled water. A diluted dip is generally a good starting place, but the dark toning on your medals might go beyond such a solution's potential.
Personally, I'm
not a fan of dark, splotchy toning as seen on these medals. I would try to restore their appearance to original. I would also place them in capsules after conserving them so as to inhibit future deterioration.