From another post:
"From previous threads here and PMs with another member:
The adapter for the K-5 and K-7 (K-AC50) works fine with the K-3, if you already have one. I have used mine and it works fine.
Also note that the K-AC1202U adapter for the
K-01 (in stock and $10 cheaper) seems to have the Switching AC Adapter D-AC120 module that the K-AC132 has, according to the In the Box info. Plus you get the adapter-to-K-01 coupler!
[Seems a bit disingenuous of Pentax to sell the K-3 adapter for a higher price, IMO.]
The new adapter seems to be needed because of changes in EU regulations regarding such things. I don't know the details, but think it has to do with environmentally friendly materials.
Cheers,
Lou