I never saw a 66, but the Teams at Little Creek VA did use 686's. I saw two at the SEAL Team display at NAS Oceana in 2004.

One was submerged in an aqarium tank. Periodically the sailors would pull it out and fire it (blanks).

I did hear that LCDR Marchenko wanted stainless S&W revolvers, but don't recall what became of that request.
Hope this helps. Regards 18DAI.