I never saw a magazine like this on an SKS???
is it just an AK conversion?

....not sure if its the same thing, but here in Australia we had two models, the SKS with the fixed mag and the SKK with detachable mag....NOT an AK but an sks with removeable mags.

Roger

Google it. There are a couple ways to get an sks to use detach mags. One has a long front extension on it.
No time right now to show you.