TC-16a converters go for peanuts S/H, compared to other AF converters. IQ is good, but they were designed for the F501 era of early AF Nikon kit, so aren't fully (AF/aperture etc) compatable with stuff today.
A rather helpful guy shows how to mod one to work the AF of newer Nikons
http://www.foolography.com/free-stuff/modify-tc-16a/
it works!
