Some variants of Yak 3 were equipped with radial engine. That should be a Yak 3U. See this page:
http://www.kotfsc.com/aviation/yak3.htmWasq, are you sure this one is a MiG 21?

When I saw it in Schatzi's gallery, I thought it is a Su-22...

The cockpit is too far ahead for a MiG 21, the negative dihedral angles of wings is not typical in MiG, but in the Su-17/22 family, such as the 2 "blades" on the wings and the double probes on nose... I may be wrong, but I think that one is a Sukhoi, not a MiG.

Here, look at this two pictures of a Polish Su 20:

EDIT: it took me a while to search some good picture of Sukhoi's, so I missed Panzzer's post... ok, not a Yak 3U 
BTW, you guys saw that jet with your eyes: does it have variable sweep wing? If so, it's not a MiG-21 without any doubt.