The 2.5" variety always seem to be in demand compared to the 4". My guess is you could shop around and find a used but functional example for around $500. However examples in the $600 range will likely be more common for condition you describe. I've watched some of the distributers on GunBroker and have seen 66's with the 2.5" barrel consistently hit the $600 and they have had a fair amount of wear on them. Just my opinion, others depending upon the area they are from may have better prices.

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