Well ... I donít think anyone knows the numbers, but .32NP is clearly much less common than .38 Special. The number of nickeled guns usually floated is 3%-5% of post-war production. Assuming 500,000-600,000 (counting serials) Detectives made during the time when .32NP was in production and 0.5% of nickel .32NP production, that gives you 2,500-3,000 guns. I think thatís the best anyone can do without going through records. Definitely not common, but not super rare.
I sold one on Gunbroker several months back. Gun was 99%, but without box. It got in the $1,300 ballpark in a penny auction.