Bought it recently from Ffordes.co.uk - a find, even if it feels a bit used :-)!

Congrats! How about combining it with the Pentax 1.7x AF converter and you'd have a 680mm focal length and auto fine focus! Having said that, the AF teleconverter works fine on my 55-300 but not on my 500mm mirror lens. The f5.6 aperture might not be fast enough.

Alas, the lens itself is very much manual (its age unknown by me), so an automatic converter doesn't help a bit ;-(!

Does anyone know why Sigma's 120-400 can't use a converter (for all other makes of cameras it can, but not with Pentax)?!

But it does! The 1.7 AF TC makes it semi-AF. You do the coarse focus manually and the TC does the fine AF.

Really?! Great News! I didn't know there was a Pentax converter that could turn a manual lens into an autofocus one!

Just took some photos with the lens, minus the TC, minutes ago!

Flickr: mr_tord_s_eriksson's Photostream